# Beyond anthropocentrism in agricultural and resource economics

Romain Espinosa, Nicolas Treich

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Romain Espinosa, Nicolas Treich. Beyond anthropocentrism in agricultural and resource economics. Australian Journal of Agricultural and Resource Economics, 2024, 68 (3), pp.541-566. 10.1111/1467-8489.12560 . hal-04645345

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# Beyond Anthropocentrism in Agricultural and Resource Economics

Romain Espinosa* and Nicolas Treich†‡

January 2024

**Abstract**

We argue that it is both possible and timely to relax the assumption of anthropocentrism in agricultural and resource economics. We advocate for the incorporation of sentientist principles by including the welfare of sentient animals within the social welfare function. To exemplify this non-anthropocentric stance, we build on our recent works that incorporate the intrinsic value of farmed animals in food production and consumption. By recognizing the externalities affecting animals, we justify the implementation of specific policies, such as a meat tax, which redistributes welfare from consumers and producers to farmed animals. Furthermore, we delve into the quantitative assessment of animal welfare and demonstrate its application to food policy, revealing the substantial economic and welfare impacts at stake. Expanding on our earlier model, we also emphasize the importance of introducing a “sentience premium” within species conservation policies. This additional consideration ensures that the conservation efforts appropriately account for the intrinsic value of sentient beings living in the wild.

**Keywords:** Anthropocentrism, agricultural economics, resource economics, animal welfare, social welfare function, biodiversity, sentience.

**JEL codes:** Q18, Q57, I31

<footnote>*CIRED, CNRS, France.</footnote>

<footnote>†Toulouse School of Economics, INRAE, France.</footnote>

<footnote>‡This paper follows from the Keith Campbell address by Nicolas Treich at the Australasian Agricultural & Resource Economics Society (AARES) conference in February 2023 in Christchurch, New Zealand. The authors thank the editor, three anonymous reviewers as well as Matt Adler, Bob Fischer, Jim Hammitt and Rafael Schütz for useful comments. Nicolas Treich acknowledges the research funding from the ANR under grant ANR-17-EURE-0010 (Investissements d'Avenir program) and from the FDIR chair at TSE-Partnership. Romain Espinosa acknowledges financial support from the ANR under grant ANR-19-CE21-0005-01. The authors declare no conflict of interest. Contact: nicolas.treich@inrae.fr</footnote>
# 1 Introduction

Anthropocentrism essentially means that humans are the only source of moral consideration. Except for a few developments, all works published in economics adopt an anthropocentric perspective and focus exclusively on the welfare of humans. In standard economic models, the key metrics for determining the social objective, namely the social welfare function (SWF), is limited to the welfare of humans. Even advances in environmental economics in the past decades have retained an anthropocentric approach, looking at climate change or the loss of biodiversity through the (long-term) damages to humankind (McShane 2018, Dasgupta 2021).

This human-centered approach in economics is morally dubious (Johansson-Stenman 2018, Carlier and Treich 2020, Fleurbaey and Leppanen 2021). Indeed, if economists seek to maximize welfare in this world, their analyses should consider all individuals that are capable of experiencing welfare, i.e., all sentient beings. The founding father of utilitarianism, Jeremy Bentham, already anticipated in the 18th century that the utilitarian framework should ultimately include all individuals capable of suffering,<fnref n="1" /> and a large body of research has since then argued that most animals are capable of welfare (Singer 1975, Dawkins 2004, Broom 2014). From a moral as well as scientific perspective, it is therefore difficult to justify the systematic disregard of animal welfare in economic analyses.

Agricultural and resource economics has not been different from the rest of economics. In these fields, animals are naturally under consideration as they are part of human consumption either directly through livestock or indirectly through the environment. However, like in the rest of the economics, animals are typically discussed as things (e.g., intermediary production goods) rather than individuals capable of welfare. Animal welfare *per se* has received no moral consideration (intrinsic value), and economists have only explored how improving animal welfare might increase the consumer surplus (instrumental value).

The intrinsic value of animals is a blind spot in environmental valuation. Typical valuation exercises rely on humans' willingness-to-pay and are thus rooted in anthropocentrism (Treich 2022). Importantly, human preferences for animals might very poorly correlate with their actual welfare, such that even an instrumental approach might fail at effectively improving animal welfare (Espinosa 2022). Attempts in environmental valuation to go beyond altruistic preferences, such as discussions about the existence value, also fail to depart from anthropocentrism as they rely on human preferences about the existence of animals or species. Once we accept that animals matter intrinsically, an important question arises about how much animals should count for, especially relative to humans in case of cross-species tradeoffs. Little progress has been made on this issue despite the increasing recognition that animals count morally. This fundamental difficulty may explain part of the resistance to developing applied non-anthropocentric research in our discipline, such as in benefit-cost analysis (Stawasz 2020).

In this paper, we challenge the assumption of anthropocentrism by expanding the scope of the social welfare function to include all sentient animals. While we build upon our previous

<footnote n="1">¹While Bentham's position regarding animal welfare may be less radical than that commonly attributed to him, Bentham saw an intrinsic worth in avoiding animal suffering, and emphasized that the key condition for moral consideration is sentience or “sensibility” (Kniess 2019).</footnote>
research efforts (Espinosa and Treich 2021, 2023), the main objective of this paper is to explore
the justifications, interpretations, and implications of this approach, rather than delve into
technical details. It is important to underscore that this study is part of an ongoing exploration
in a rapidly evolving and interdisciplinary field. Therefore, this paper should be primarily
regarded as an introductory overview of the topic, recognizing that it may require regular
updates as scientific knowledge progresses.

The paper delivers a simple message: We argue that it is possible and that it is time to relax the assumption of anthropocentrism in economics. We further argue that the benefits of doing so are likely to be significant. To illustrate how we can progress, we present a simple non-anthropocentric model of animal use. We in turn deliver a few insights for agricultural and environmental policymaking. We calibrate some key parameters of the model using recent survey studies and present an application showing that the monetized impacts of the externality on animals can be important (Kuruc and McFadden 2022, Espinosa and Treich 2023). Hence this paper is relevant both for economic theory and empirical analyses.

The outline of the paper is the following. We first discuss the central concept of sentience (section 2), and then how one can modify the SWF to include sentient animals (section 3). We then present and study a very simple model of animal production and consumption, and explore some of its policy implications (section 4). We also discuss studies, methods and challenges regarding the assessment of animal welfare, and illustrate our approach with an application (section 5). We finally present a simple non-anthropocentric model of species' conservation (section 6), before concluding (section 7).

2 Sentientism

2.1 Arguments in favor of sentientism

Schematically, we can distinguish four main sets of entities to be morally valued. First, one
could consider that only humans deserve moral consideration. As we mentioned above, this
anthropocentric approach has been almost universal in economics. Interestingly, this approach
is almost always implicit, in the sense that scholars do not try (or even think) to justify why
the scope of their work is limited to human welfare. For instance, numerous works in agricul-
tural economics address husbandry productivity, food security, or negative externalities of the
food system without mentioning animal welfare. Sometimes, anthropocentrism is explicitly
justified, as in the last Dasgupta Review on the economics of biodiversity (Dasgupta 2021),
but the justification used may be challenged (Treich 2022).

It is likely that economists suffer from a status quo bias here: the anthropocentric norm
is so well-established in the economic discipline that economists do not seem to see that the
non-inclusion of animals in the social objective function is equivalent to actively refusing to
consider the animals’ interests. This prevailing anthropocentrism can be attributed, in part,
to our instinctive moral intuitions that consistently favor our own species. Additionally, the
influence of political forces driven by human concerns skews our research agenda, perpetuating
a human-centered approach. This influence is particularly evident in agricultural and resource
economics.

The most common approach to justify anthropocentrism is human exceptionalism (Gruen 2017). This line of argument consists in arguing that humankind possesses distinct capacities that other animals do not have and that these capacities are those that grant moral status. It is true that humankind stands out in several manners in the animal kingdom but the justification of anthropocentrism on human exceptionalism is fragile in two ways. First, the frontier between humans and other animals is much thinner than what we used to think. Rather than opposing humans and other animals, the current state of scientific knowledge indicates that there are biological continuities between humans and animals (Sekar and Shiller 2020). Indeed, it is difficult to single out one capacity that would be exclusive to humankind. Second, even if we recognize that some capacities are specific to humankind, it is unclear whether these capacities justify moral status on their own. For instance, while some philosophers argue that only humans face the problem of normativity, it is not clear why the capacity to think about the good and the bad should grant moral status. Most people would indeed still grant moral status to a human who is not capable to achieve this level of abstract thinking (e.g., newborns).

The second possible normative approach consists to grant moral status to all sentient beings. This view is often called the sentientist (or pathocentric) approach. In its narrowest sense, sentience refers to the minimal consciousness level to be capable to have subjective experiences of the world, also called valenced consciousness. Broom (2014) defines sentience as “having awareness and cognitive ability necessary to have feelings”. From an economic perspective, we can define sentience as the capacity to undergo different states of welfare. Unlike the anthropocentric standpoint, the sentientist approach asserts that moral status should be granted based solely on an individual's capacity to experience welfare. In the words of Bentham (1780), the crucial question is not whether animals can talk or think, but rather whether they can suffer. The sentientist viewpoint has a rich philosophical tradition, with proponents such as Rousseau (1755), Bentham (1780), Singer (1975, 2011), and Regan (1983).

A third possibility is to grant moral status to all living things, which is called the biocentric approach. Proponents of biocentrism argue that moral consideration should be extended not only to sentient animals but also to non-sentient living entities such as plants, fungi, or bacteria for instance. Last, some argue for a fourth approach which would consist in assigning moral value to ecosystems (ecocentric view). In this perspective, moral status should be granted to non-living things as well, such as air, rivers, or mountains (see, e.g., Leopold (1949) or Callicott (1989)).

In this paper, we argue for the adoption of a sentientist approach for at least four reasons. First, economics is largely a welfarist discipline, i.e., economists primarily care about welfare. Positive economics often investigates the changes in the welfare of agents (consumers, producers, voters, etc.), and normative economics seeks to maximize the social objective function that depends on the welfare of agents. Second, the adoption of the sentientist approach by economists would also align the field with late developments in the utilitarian philosophy regarding antispeciesism (Singer 1975, 2011; Horta 2010; Johansson-Stenman 2018; Treich
2022). Third, while sentientism is a natural development of the utilitarian framework, bio-centrism and ecocentrism represent larger and more uncertain conceptual gaps. Animals like humans are capable of welfare, and we might attempt to rank different situations relative to their well-being. The moral valuation of entities that are not capable of welfare seems more distant from standard economic theory (see Fleurbaey and Leppanen 2021 for a discussion). Fourth, even if we consider that biocentrism or ecocentrism are the most preferable approaches, the adoption of the sentientist approach can be seen as a first and necessary step toward a more encompassing normative framework.

## 2.2 Challenges of sentientism

One important challenge of the sentientist view is to precisely characterize the moral community (Fischer 2021), i.e., the set of beings who deserve moral consideration. As Sidgwick (1893) writes: “We have next to consider who the ‘all’ are, whose happiness is to be taken into account. Are we to extend our concern to all the beings capable of pleasure and pain whose feelings are affected by our conduct?”.

It is now well-established in animal sciences that all mammals and birds are sentient (e.g., Cambridge Declaration on Consciousness, Low et al. 2012). A more recent but solid body of evidence has also shown that fish and cephalopods are sentient (Baars 2001, Edelman et al. 2005, Brown 2015). While the entomology literature has historically considered that insects cannot feel pain, there is still scientific uncertainty about this, but more and more recent evidence tends to suggest the contrary (Lambert et al. 2021; Gibbons et al. 2022).

The sentientist approach is thus likely to encompass almost all animal lives. Some argue indeed that because all animals are, by definition, animated, they need to be able to perceive their environment to move in it. However, the current sentientist approach does not include plants and is unlikely to do so. According to the current state of scientific knowledge, plants are not thought to possess consciousness or feelings. In a recent synthesis paper, Taiz et al. (2019) conclude indeed that “the likelihood that plants, with their relative organizational simplicity and lack of neurons and brains, have consciousness to be effectively nil”. While plants have complex cell contacts and signaling mechanisms, they indeed lack the central characteristics that make sentience among animals (Draguhn et al. 2020, Mallatt et al. 2021).

Sentientism is probably the main normative alternative to anthropocentrism (Beausoleil 2020, Newman et al. 2017). It is also linked to the increasingly popular notion of (anti)speciesism. Normative speciesism is a doctrine that considers that individuals should be granted different moral values based solely on their species membership (Caviola et al. 2019). Singer (2011) describes a speciesist person as someone who ‘allows the interests of his own species to override the greater interests of members of other species. On the contrary, an antispeciesist approach embraces the notion of equal consideration of interests. This normative principle entails that similar interests should receive similar normative consideration independently of the species membership of the affected individuals. See Kagan (2019) for a critical discussion of the concept.

In economics, it is natural to assume that antispeciesism implies equal weights assigned
to the utility<fnref n="2" /> of different sentient beings in the SWF. Importantly, although the sentientist approach entails that we should not discriminate against species membership, it obviously does not imply that all individuals should generally be treated in the same way. Some animals might indeed be capable of realizing more welfare than others. One critical challenge is thus to measure and compare the possible range of welfare states that animals from different species can experience (inter-species comparison problem). Addressing this challenge requires a high level of interdisciplinary work that researchers have just started. Natural sciences such as ecology or ethology have not been primarily interested in measuring social welfare as we routinely do it in economics for humans. Previous attempts to work in this direction, such as the wish to develop the new field of “welfare biology” by Ng (1995), have had very limited success so far.

In recent years, however, a renewed and stronger interest in defining proper empirical metrics of animal welfare across species. The effective altruism movement has largely contributed to the development of this field as effective altruists look for metrics to identify the most welfare-enhancing actions to undertake. In particular, the research team led by Bob Fischer of Rethink Priorities undertook a large project to quantify animal welfare. In this project, researchers identified empirical proxies for welfare (hedonic and cognitive proxies) and reviewed the literature to identify evidence of these proxies across 11 farmed species (including pig, chicken, shrimp, and bees). The capacities include parental care, self-medication, depression-like behavior, or emotional contagion for instance. Results displayed in Figure 1 show four important points (Fischer 2022). First, some animals like pigs display an important number of hedonic proxies. Second, research is still scarce for many species such that much work is needed in animal sciences. Third, it is much more complex to show that animals from a species are not capable of something than showing that they are. Last, it is very likely that there exists a continuum of species in terms of capacities. While the concept of sentience is binary, animals are likely to experience welfare states with different levels of intensity.

The antispeciesist approach does not weigh differently similar interests based on the species membership but recognizes that different species might have different ranges of possible welfare. Economists, like effective altruists, are then interested in obtaining scores that account for this heterogeneity in the capacity to experience welfare. One important challenge is to obtain a metric that reflects this heterogeneity, which can be coined “utility potentials” (Budolfson and Spears 2020, Espinosa 2022). The research effort undertaken by scholars such as Fischer (2022) contributes to the definition of these weights with the longer-term objective to make effective cross-species welfare comparisons.

# 3 The social welfare function

In this section, we discuss how to include sentient animals in the social objective, namely into the social welfare function (SWF). In public economics and social choice, the SWF is designed

<footnote n="2">²The term “utility” may have different interpretations in economics (e.g., hedonic wellbeing, preference satisfaction). We will be more precise in section 5 about our interpretation when discussing the method to estimate animals’ utility.</footnote>
<figure><img src="image_2.png" /><figcaption>Figure 1: Hedonic proxies for animal welfare</figcaption></figure>

Source: Rethink Priorities

to adhere to certain desirable normative properties, such as Pareto efficiency, anonymity, and separability. In the context of utilitarian economics, social welfare is defined as the aggregate
of individual utilities, possibly after applying certain transformations. The choice of the SWF's normative assumptions can significantly influence the ranking of different policies. Therefore, a crucial step in advancing a sentientist approach within public economics involves discussing and examining the normative criteria that should govern the SWF.

We can distinguish between two main possibilities to include animals in the SWF. First, the SWF can consider human welfare only. In this case, animal welfare might still affect the SWF (and the ordering of policies) if humans display altruistic preferences for animals: pet owners will be better off whenever their pets are better off. This indirect approach is well-established in economics (e.g., Norwood and Lusk 2011) but remains anthropocentric (i.e., the source of social welfare is humans). Second, the SWF may directly consider the welfare of all sentient beings. In this direct approach, the welfare of animals matters per se, not through the preferences of humans (i.e., animals have an intrinsic value). We adopt this direct, non-anthropocentric approach in the rest of the paper. Note that, while the two approaches may be combined, it raises important conceptual issues (such as the double counting of animal welfare) that are beyond the scope of this work.

What properties should a non-anthropocentric SWF have? A few works have started exploring this question but the literature is still scarce. The inclusion of animals in the SWF raises important normative issues (Fleurbaey and Leppanen 2021). In a seminal paper, Blackorby and Donaldson (1992) propose a critical-level SWF in which humans' and animals' interests receive equal consideration. Recently, Zuber et al. (2022) provide the first axiomatic characterization of a multi-species SWF. They obtain various representation theorems based on separability and anonymity axioms, leading to an additively-separable utilitarian SWF for multispecies. In the case of multi-species SWF, the concept of anonymity becomes twofold: intra-species anonymity ensures that individuals of the same species receive equal consideration while inter-species anonymity ensures that only utility levels matter (and not the species).

Formally, let us consider total utilitarianism,<fnref n="3" /> and let $u_{is}$ the utility of individual $i$ in species $s$, with $a_s$ the “moral weight” of species $s$ in the SWF:

$$ \sum_{s} a_{s} (\sum_{i} u_{is}) \qquad (1) $$

This simple formulation permits to emphasize two opposite cases:

- anthropocentrism: $a_s = 1$ when $s$ is the human species, 0 otherwise; and

- antispeciesism: $a_s = 1$ for all sentient species $s$.

The assumption of antispeciesism, i.e., $a_s = 1$ for all sentient species $s$, simply reflects the principle of equal consideration of interests (Singer 1975): similar interests as captured by a similar change in the utility function for different species have the same impact on the social

<footnote n="3">³Note that total utilitarianism is a special case of critical-level utilitarianism where a life positively contributes to social welfare if its net utility is above zero.</footnote>
objective. Note that antispeciesism corresponds to the standard anonymity axiom in a multi-species context. In other words, it formalizes the ethical attitude of impartiality (Adler 2019): each affected individual's well-being is given an equal moral weight in the social objective. We employ the expression "moral weight" here because the weight given to species *s* in the social objective might possess a moral underpinning (Browning 2023), even for values *a*<sub>s</sub> < 1. As an illustration, Kagan (2019) proposes a hierarchical moral theory where animals count less than humans. However, note that this weight *a*<sub>s</sub> given to species *s* in the social objective could also reflect some political views.

Johansson-Stenman (2018) develops a survey study about moral weights. In his survey, Swedish participants are asked to which extent the suffering in an animal should count in public decisions relative to “an equal amount of suffering” in a human. Participants could choose one of the following answers: animal suffering should not count, it should count through human preferences only (i.e., the indirect approach), it should be taken into account to a certain extent, a fairly high degree, to a degree equal to human suffering, or to a very high degree. Interestingly, the answers in Table 1 show that the antispeciesist view (i.e., equal consideration of suffering reduction) is the dominant view, as about one-half of participants support this view.

<table><caption>Table 1: A survey study about the non-anthropocentric SWF (Johansson-Stenman 2018)</caption><caption>Response distribution for the following question: Society can reduce animal as well as human suffering through various, usually costly, measures. To be able to prioritize, we need to know how great a weight society should place on reducing suffering in an animal (such as a cow) compared with reducing an equal amount of suffering in a human. Which of the following statements is most in accordance with your opinion regarding the weight that should be given to animal suffering in public decisions?</caption><tbody><tr><td>Animal suffering should not count at all in public decisions</td><td>0.8%</td></tr><tr><td>Animal suffering should not count per se. However, some people suffer when knowing that animals suffer, and this should be taken into account in public decisions</td><td>3.2%</td></tr><tr><td>Animal suffering should be taken into account to a certain extent in public decisions, even when no human beings suffer when knowing that animals suffer. However, animal suffering should be given much less weight than human suffering</td><td>13.2%</td></tr><tr><td>Animal suffering should be taken into account to a fairly high degree in public decisions, even when no human beings suffer when knowing that animals suffer. However, animal suffering should be given somewhat less weight than human suffering</td><td>30.3%</td></tr><tr><td>Animal suffering should be taken into account to a degree equal to human suffering in public decisions, even when no humans suffer when knowing that animals suffer</td><td>49.3%</td></tr><tr><td>Animal suffering should be taken into account to a very high degree in public decisions, even when no human beings suffer when knowing that animals suffer. Animal suffering should be given more weight than human suffering</td><td>3.2%</td></tr></tbody><tfoot><tr><td colspan="2">Note: Number of observations = 1072.</td></tr></tfoot></table>

This discussion is informative about the normative inadequacy of lexicographic human-animal preferences. Under a lexicographic rule, the social planner first evaluates alternatives on the most important attribute, and if there are ties, on the second-most important attribute, and so on. Lexicographic human-animal preferences mean that humans' welfare is the most important attribute that would decide everything, but if the situation is equal for humans then an improvement of the welfare of animals is always better. In other words, such a "human-first" approach would not favor any trade-off between humans and animals' welfare. This is not what the survey study above suggests, and this approach stands in contrast with an antispeciesist view. In fact, animal-welfare-enhancing policies generally imply a trade-off between human and animal welfare, at least indirectly (e.g., the resources devoted to the animal-welfare policy could have been used for another human-relevant policy). Lexicographic
human-animal preferences would in practice amount to ignoring the intrinsic value of animals
and be virtually equivalent to an anthropocentric approach. We thus rule out this approach
in the following.

As we said, the SWF approach is supposed to respect various properties that are viewed
as normatively appealing. Going back to the famous Arrow's impossibility theorem, it usually
respects universality, nondictatorship and monotonicity. Importantly, it does not respect the
independence of irrelevant alternative property, namely the property that the social preference
between two policies x and y should depend only on the individual preferences between x
and y. Indeed, the SWF approach requires more information than that about individual
preferences, as it typically requires information about interpersonal wellbeing comparisons.
This is the most controversial aspect of the SWF approach. Although we do not discuss in
this paper the classical issue of within-species (human) utility comparison (see, e.g., Adler
2019), we will return later to this issue to discuss interspecies utility comparison.

At this point, it is useful to note the subtle difference between sentientism and welfarism. Sentientism establishes the moral community by recognizing that all sentient beings deserve moral consideration. In this setting, we acknowledge that all sentient individuals have the capacity for welfare. Welfarism posits that societal goals are exclusively tied to welfare considerations. Nevertheless, welfarism and sentientism are not interchangeable concepts. It is indeed conceivable to envision a deontological (i.e., non-welfarist) but sentientist approach, where a set of principles or rights is defined to guide interactions among all sentient beings. For instance, Newman et al. (2017, chapter 8) distinguishes "utilitarian sentientism" (Singer 1975, 2011) from "rights-based (deontological) sentientism" (Regan 1983). It is also possible to have an anthropocentric (i.e., non-sentientist) welfarist approach as it has been historically the case in economics.

Last, let us note that choices regarding animals often affect the number of existing animals, which has important implications with respect to population ethics. This is the case for instance when it comes to meat consumption or biodiversity conservation. When the size of the population varies, specific issues can emerge with the aggregation of welfare. Common SWFs such as total utilitarianism can have morally troublesome consequences under variable populations (e.g., repugnant conclusion, sadistic conclusion; see Blackorby et al. 2005), which can become even more complex in case of multispecies SWFs. A common way to address this question is by studying different normative settings. This study is beyond the scope of this paper but readers must keep in mind that policy recommendations with variable populations are sensitive to the axiomatic choices in the SWF. In the rest of the paper, we use total utilitarianism.

4 A simple non-anthropocentric model

Building on the previous sections, we now develop a simple model using a non-anthropocentric utilitarian SWF.
## 4.1 Optimal animal consumption

We study in this section a simple model as an illustrative example of a non-anthropocentric economic model. We consider a utilitarian SWF with two species (i.e., humans and animals). In this model, humans derive a benefit from the consumption of animals. We study the socially optimal number of animals to consume given that the welfare of animals matters. We build on Blackorby and Donaldson (1992) and Espinosa and Treich (2021, 2023).

The social objective is given by:

$$U(n) = u(n) - c(n) + anv \quad (2)$$

where $n$ is the number of animals consumed per human, $u(n)$ is the human utility derived from animal consumption, assumed to be increasing and concave, $c(n)$ is the animal production cost function, assumed to be increasing and convex, $v$ is the animal utility, and $a$ is the antispeciesism level.

The novelty in this model is that the welfare of animals is directly included in the social objective. Hence, the SWF is non-anthropocentric. Note that we consider here only animals whose existence depends on human consumption. We interpret it as a model of meat consumption but it can be seen more generally conceived as a model of animal use, including for instance animal testing. For simplicity, we assume full antispeciesism for the rest of the paper, i.e., $a = 1$.

We focus on interior solutions. The socially optimal consumption level $n^*$ is characterized by the following first-order condition (FOC):

$$u'(n^*) = c'(n^*) - v \quad (3)$$

This condition entails that, at the social optimum, the marginal benefit of consuming an animal is equal to its marginal cost of production minus the utility level of one animal. The last term reflects the fact that bringing an additional animal into existence for consumption is socially beneficial (resp. detrimental) if the animal's life is worth living $v > 0$ (resp. not worth living $v < 0$).<fnref n="4" />

As is standard, we can compare the social optimum with the market equilibrium outcome. Let $p$ be the equilibrium price of meat. Consumers maximize their utility $u(n) - pn$ over the number of animals $n$ while producers maximize their profits $pn - c(n)$ over $n$. This leads to the standard equilibrium condition:

$$u'(n_e) = c'(n_e) \quad (4)$$

where $n_e$ is the number of animals consumed at the market equilibrium.

This last equality reflects the fact that, at the market equilibrium, the marginal benefit of consuming an animal is equal to its marginal production cost. If animals had no intrinsic value, this would simply characterize an efficiency condition, and provide an illustration of the

<footnote n="4">⁴Note again that this particular outcome results from total utilitarianism.</footnote>
First Welfare Theorem in our simple economy. However, if we socially value animal welfare, the externality imposed on animals' well-being generates an inefficiency. Indeed, at the market equilibrium, there is i) over-consumption of animals $n_e > n^*$ if their life is not worth living $v < 0$, and ii) under-consumption of animals if their life is worth living $v > 0$.

This last result is akin to the “logic of the larder” argument (Salt 1917) according to which we would do animals a favor by eating them because they would otherwise not exist. In this view, meat consumption should be encouraged because animal farming would generate a positive externality (case ii). Note that the result shows that the rationale for the logic of the larder critically depends on whether the animal’s life is worth living or not. This question has generated a longstanding philosophical debate: see for instance Matheny and Chan (2005) and Visak (2013).

In Espinosa and Treich (2021), we contribute to this debate by presenting survey data. In this work, we introduce survey participants to information about the rearing conditions of broilers in France under different husbandry systems. We focus on broilers as they represent about 80% of the terrestrial animals killed for meat production in France. In the survey, we ask participants whether they consider that the life of the broilers living in each husbandry system presented is worth living. We collected data from four types of participants: students, experts in animal ethics, experts in farmed animals (i.e., in poultry, bovine, and porcine farming), and animal activists. We found that almost all of our respondents believe that the life of broilers is not worth living under the most prevalent husbandry systems in France (see Table 2).

In a recent original work, Bruers (2022) also contributes to this debate by exploring people's views about whether the lives of farmed animals are worth living. In his thought experiment, consumers are asked whether they would like to experience the life of an animal during their sleep. Participants would experience all feelings of the animal (from birth to death) but would not remember any of it after they later wake up. Positive willingness-to-pay (WTP) reflects people's views that the animal's life contributes positively to social welfare, while positive willingness-to-accept (WTA) indicates that we need to pay people for them to accept to experience the animal's life. In the survey, most of the Belgian consumers interviewed reported a positive WTA and a negative or null WTP for broilers and pigs, which suggests that they believe that these animals' lives are not worth living in the current rearing conditions.

## 4.2 Optimal policy

The theoretical results above indicate that animal consumption at the market equilibrium is not socially optimal. We now investigate strategies that can help restore efficiency. To start with, decentralized mechanisms like Coasian bargaining sound elusive here. Humans cannot contract with animals as the latter lack the necessary cognitive capacities to do so and do not take part in monetary transactions. Public intervention (on behalf of animals) seems necessary to solve the market failure. In what follows, we explore the impact of a fiscal instrument on social welfare. Following Espinosa and Treich (2023), we apply a fiscal levy $t$
<table><caption>Table 2: Assessment of whether a broiler's life is worth living by husbandry system (Espinosa and Treich 2021)</caption><thead><tr><th colspan="5">Broiler farming systems (indoor rearing)</th></tr><tr><th>Density</th><th>20 chickens/m2</th><th>14 chickens/m2</th><th>14 chickens/m2</th><th>8 chickens/m2</th></tr></thead><tbody><tr><th>Natural light</th><td>No</td><td>Yes</td><td>Yes</td><td>Yes</td></tr><tr><th>Perches</th><td>No</td><td>Yes</td><td>Yes</td><td>Yes</td></tr><tr><th>Pecking objects</th><td>No</td><td>Yes</td><td>Yes</td><td>Yes</td></tr><tr><th>Outdoor access</th><td>No</td><td>No</td><td>No</td><td>Yes</td></tr><tr><th>Number of chickens on the farm</th><td>&gt;1000</td><td>&gt;1000</td><td>&gt;1000</td><td>&gt;1000</td></tr><tr><th>Stunning before slaughter</th><td>No</td><td>Yes</td><td>Yes</td><td>Yes</td></tr><tr><th>Age at slaughter</th><td>40 days</td><td>40 days</td><td>60 days</td><td>80 days</td></tr><tr><th>Transport time to slaughterhouse</th><td>8h</td><td>6h</td><td>3h</td><td>3h</td></tr></tbody><tfoot><tr><th colspan="5">Share who believes that life is worth living (in %)</th></tr><tr><th>Activists</th><td>0</td><td>0</td><td>0</td><td>1.6</td></tr><tr><th>Animal-ethics experts</th><td>0</td><td>0</td><td>0</td><td>0</td></tr><tr><th>Farm-animal experts</th><td>5.3</td><td>10.5</td><td>15.8</td><td>63.2</td></tr><tr><th>Students</th><td>0.8</td><td>2.5</td><td>4.9</td><td>25.6</td></tr></tfoot></table>
to meat consumption.

When a levy $t$ is applied, the optimal animal consumption level chosen by consumers and producers, denoted $n(t)$, is characterized by the following FOC:

$$u'(n(t)) = c'(n(t)) + t \quad (5)$$

The social problem then amounts to choosing $t$ to maximize<fnref n="5" />:

$$u(n(t)) - c(n(t)) + n(t)v \quad (6)$$

yielding:

$$u'(n(t)) = c'(n(t)) - v \quad (7)$$

Hence, by combining the two last FOCs above, we can immediately infer that the socially optimal animal-welfare levy equals $t^* = -v$. Note that the levy is positive when animal life is not worth living, and negative (i.e., it is a subsidy) when life is worth living. This result is intuitive following what we said in the previous section: we must tax (resp. subsidize) animal-based products when they generate negative (resp. positive) externalities on the animals.

Unsurprisingly, our analysis of how to address the externality on animals shows that it is optimal to implement a sort of Pigouvian fee. The levy is indeed equal to the marginal social value of consuming one additional animal so that the consumers and producers fully internalize the externality on the animals. Since there is no heterogeneity across consumers and producers and no distortionary effects of taxation, it is immediate that the levy permits to reach the non-anthropocentric first-best.

Using a standard price-quantity setting, Figure 2 shows the welfare impact of the levy when it is a tax, i.e. $t^* = -v > 0$. The hatched areas represent the classical deadweight loss, i.e., the loss in human welfare resulting from the reduction in the consumers' and producers' surpluses. The welfare loss is driven by the decrease in the number of animals consumed/produced after the introduction of the meat tax.

Importantly, the yellow rectangle represents the gain in animal welfare: $-v(n_e - n^*) > 0$. This gain is due to the non-worth-living animal lives that are avoided because of the decrease in meat consumption due to the introduction of the tax. This is a net gain for animals since, without a tax, $n_e - n^*$ additional animals would have lived, and this would have reduced welfare because these animals have a negative net utility, $v < 0$.

The animal welfare levy thus induces a redistribution of welfare from humans to animals and increases overall social welfare. Note that this is an unusual welfare redistribution induced by the policy, since the beneficiaries are the nonexisting animals that would have existed without the policy. This example also illustrates the political challenge to reaching the socially optimal situation in an economy in which humans would have full political power. Why would humans accept to pay an extra price for meat for animal welfare considerations (i.e., to trade human welfare off with animal welfare)? In a human-only setting, Pareto improvement can

<footnote n="5">⁵We assume that the revenues of the levy are given back to the consumers through lump-sum monetary transfers.</footnote>
<figure><img src="image_3.png" /><figcaption>Figure 2: Welfare impact of the animal welfare levy (Espinosa and Treich 2023)</figcaption></figure>

be achieved as soon as there is room for Kaldor-Hicks improvement through wealth transfers. But what about human-and-animal settings where animals cannot transfer wealth back to humans?

The model above is obviously very simple. Its main objective was to illustrate a non-anthropocentric approach, and in particular to emphasize the deviation that induces the inclusion of animals in the SWF compared to the most standard economic approach. One important limitation is that we assumed that the utility level of animals, i.e., $v$, is fixed. Hence, we have not studied the possibilities of either private or public effort to directly improve animal welfare through a change in $v$. See Espinosa and Treich (2023) and Eichner and Runkel (2023) for an analysis of this aspect. Another important limitation is that we did not explore the heterogeneity of consumers and producers as well as that of animals within and/or across species.

# 5 Assessing animal welfare

We now discuss studies, methods and challenges regarding the assessment of the animal's utility function $v$ defined in the previous section, and illustrate our approach with an application.

## 5.1 Existing studies and methods

In animal sciences, there exist numerous measures of animal welfare, especially for farmed animals (Broom 2014). They include for instance records of mortality and injury rates or
of movement difficulties or stereotypies and various other physiological measures such as increased heart rate, adrenal activity, or reduced immunological response. There exist in particular a large literature on pain assessment, and more and more works on plays, normal behaviors, and happiness in animals. An important challenge however is to find a way to transform these measures into a general indicator of welfare (see below).

In economics, the most standard method to assess welfare is to resort to revealed preferences. Interestingly, there exists a (small) literature on revealed preferences for animals (Dawkins 2004). For instance, Matthews and Ladewig (1994) explore the choices and trade-offs of pigs for food, contact with a partner animal, and outdoor access. Along this line, Mason et al. (2001) show that farmed minks would pay high costs to perform a range of natural behaviors such as swimming. Note that farmed minks' good health and breeding success show adaptation to captivity. Hence, this study emphasizes a significant reduction in welfare associated with captivity that pure physiological approaches may not capture well.

The application of the revealed preferences approach to animals holds promise; however, incorporating this approach into standard policy evaluation tools like benefit-cost analyses (BCA) presents challenges. The revealed preferences approach faces the usual problem that choices may be inconsistent, and thus a poor indicator of welfare. Interestingly, several works have shown that animals' choices seem to follow similar inconsistency patterns as those observed in humans (Ainslie and Herrnstein 1981, MacDonald et al. 1991). Further, it seems likely that in many contexts animals display more choice inconsistencies than humans due to limited cognitive abilities.

In this paper, we adopt another approach, namely the SWF approach (Adler 2012, 2019); see Section 3. The idea underlying this approach is to translate possible outcomes into welfare levels among the affected individuals, represented by interpersonally comparable well-being numbers. Needless to say, there is a long tradition in economics that disputes interpersonal comparison (Adler 2019), and the challenge here seems much more severe since this comparison concerns individuals across different species. We believe, however, that some progress can be made by combining some models developed in animal sciences and in human health, and by integrating those models into the SWF approach, as we now explain.

## 5.2 Models of animal welfare

Researchers have sought to capture animal welfare through several generations of models. First, according to Brambell (1965)'s Five-Freedom model, there are five freedoms crucial to ensure animal welfare, i.e., i) freedom from thirst, hunger, and malnutrition, ii) freedom from discomfort and exposure, iii) freedom from pain, injury, and disease, iv) freedom from fear and distress, and v) freedom to express natural behavior. This list was initially intended to serve as a checklist for humans to assess the advantages and disadvantages of various husbandry methods. The World Organization for Animal Health (WOAH), for example, endorses the Five-Freedom model, which is one of the most popular models in use today.

Later, animal specialists contested the Five-Freedom approach and created the Welfare Quality model. The approach was criticized by the experts for being too vague, having over-
lapping components, and lacking implementability. The next step was to design an animal welfare framework that could be used for any species of farmed animals and would be “scientifically valid and widely accepted by stakeholders” (Bonde et al. 2009). The Welfare Quality framework retained all components of the Five-Freedom model and divided them into twelve orthogonal subcriteria. The behavioral aspects of animal welfare were also given more attention in this new paradigm. In the European Union, there has been a lot of interest in the Welfare Quality concept, and thorough protocols have been devised to evaluate it in farms (for instance, Welfare Quality - Assessment protocol for laying hens, Welfare Quality Network 2019).

However, the two first generations of models face important limitations. One main critique to the Five-Freedom approach is that it solely analyzes potential violations of the animals' freedoms, i.e., it is primarily concerned with preventing negative experiences for the animals. As a result, animal welfare is defined as the lack of negative experiences. Yet, as Mellor (2016) points out, reducing pain does not always result in positive welfare states. The Welfare Quality model has also been criticized for its limitations. First, as the authors of the framework explain themselves, the approach considers animal welfare variables that stakeholders find acceptable, potentially leading to a biased perspective on animal welfare. Second, Mellor (2016) asserts that animal welfare models should discriminate between what is necessary for the animals' life (survival-critical negative impacts) and what is not (situation-related affects). Both models fail to distinguish between the two kinds of impacts. Finally, we can note that the Welfare Quality model's implementation methods do not evaluate the well-being of a single animal but rather the aggregate welfare at the farm. For example, the index for lameness is a non-linear transformation of animal well-being. It implies that the welfare of an animal is considered differently based on the welfare of the other animals on the farm. This might be an undesirable way to value welfare from a social choice perspective (i.e., the welfare of a single animal will be considered differently depending on the situation of the farm it is reared in).

More recently, Mellor and co-authors endeavored to address these issues and proposed an alternative model, i.e., the Five-Domain model (see Figure 3). The Five-Domain model defines animal welfare as a combination of physical/function domains (diet, environment, health, behaviors) and affective domains (mental state). The model distinguishes between survival-related and situation-related elements. It gives significant importance to mental states, which also account for pleasurable experiences (e.g., drinking pleasures, affectionate sociability, excited playfulness, sexual gratification). Green and Mellor (2011) suggest a four-tier quality of life scaling system based on the Five-Domain framework: (i) a life not worth living, (ii) a life worth avoiding, (iii) a point of equilibrium, (iv) a life worth living, and (v) a good life.

In our eyes, one of the most important contributions of the Five-Domain model is to put animals' emotional states at the heart of animal welfare assessment. For instance, the Five-Freedom framework would negatively view a situation where a broiler has limited access to food because it violates the first freedom. The Five-Domain framework would also add that it is not only the lack of access to food that matters but the hunger experienced by the broiler.
<table><caption>Figure 3: The Five-Domain framework</caption><thead><tr><th colspan="6">Physical/Functional Domains</th></tr><tr><th colspan="6">Survival-Related Factors</th></tr><tr><th colspan="2">1: Nutrition</th><th colspan="2">2: Environment</th><th colspan="2">3: Health</th><th colspan="2">4: Behaviour</th></tr><tr><th>Negative</th><th>Positive</th><th>Negative</th><th>Positive</th><th>Negative</th><th>Positive</th><th>Negative</th><th>Positive</th></tr></thead><tbody><tr><td>Restricted water & food; poor food quality</td><td>Enough water & food; balanced and varied diet</td><td>Uncomfortable or unpleasant physical features of environment</td><td>Physical environment comfortable or pleasant</td><td>Disease, injury and/or functional impairment</td><td>Healthy, fit and/or uninjured</td><td>Behavioural expression restricted</td><td>Able to express rewarding behaviours</td></tr><tr><th colspan="8">Affective Experience Domains</th></tr><tr><th colspan="8">5: Mental State</th></tr><tr><th colspan="2">Negative Experiences</th><th colspan="2">Positive Experiences</th><th colspan="4"></th></tr><tr><td>Thirst</td><td>Breathlessness</td><td>Anger, frustration</td><td>Drinking pleasures</td><td>Vigour of good health & fitness</td><td>Calmness, in control</td><td></td><td></td></tr><tr><td>Hunger</td><td>Pain</td><td>Boredom, helplessness</td><td>Taste pleasures</td><td>Reward</td><td>Affectionate sociability</td><td></td><td></td></tr><tr><td>Malnutrition malaise</td><td>Debility, weakness</td><td>Loneliness, depression</td><td>Chewing pleasures</td><td>Goal-directed engagement</td><td>Maternally rewarded</td><td></td><td></td></tr><tr><td>Chilling/overheating</td><td>Nausea, sickness</td><td>Anxiety, fearfulness</td><td>Satiety</td><td></td><td>Excited playfulness</td><td></td><td></td></tr><tr><td>Hearing discomfort</td><td>Dizziness</td><td>Panic, exhaustion</td><td>Physical comforts</td><td></td><td>Sexually gratified</td><td></td><td></td></tr><tr><th colspan="8">Welfare Status</th></tr></tbody></table>

In other words, what matters for welfare is not the objective situation (lack of access to food) but the associated feeling experienced by the animal. This approach to animal welfare is much more consistent with the economic approach in which the experienced level of well-being is what really matters.

## 5.3 Utility potentials

The above models of animal welfare can help us assess animal well-being on a scale from the worst to the best welfare states. However, numerous scholars have argued that the range of experienced welfare might differ across species. In other words, an ant might experience welfare on a much more narrow scale than an elephant. The rationale is that, if welfare is mostly defined by emotional states (i.e., what the animals *feel*), animals that are capable to experience a larger range of emotional states are likely to experience welfare on a broader scale (i.e., more extreme well-being statuses). An elephant is, for instance, able to experience all (or most of) the emotions experienced by ants but is also capable to experience more complex emotions that the ant is not capable to experience.

The concept of *utility potentials* has been introduced to explore the variation in the capacity to experience well-being among different beings. Budolfson and Spears (2020) have provided one of the initial discussions on this concept within economic theory. They highlight that a significant challenge in overcoming anthropocentrism is the ability to quantify animal welfare using a common scale comparable to human well-being. This challenge arises from the difficulty of making interspecies comparisons, that is, comparing the well-being of humans and individuals from nonhuman species. The authors build on Wong (2016) who considers that the key issue for interspecies comparisons consists in estimating the well-being capacity of individuals of nonhuman species relative to the well-being of humans.

Budolfson and Spears (2020) suggest utilizing a proxy measure to approximate utility
potentials. In their approach, they employ the number of neurons in the brain of individuals within a species as an empirical proxy. It is important to note that the authors themselves acknowledge the limitations of this proxy measure. However, they argue that it serves as a valuable initial point of reference since it captures the substantial distinctions between broad groups of species, such as mammals versus insects. Furthermore, the advantage of using this proxy is its wide availability across a significant number of species. The authors then compute the *utility potential* of animals of species *s* (which we note $\phi_s$) as the ratio of the proxy for species *s* over the proxy for humans *h*: $\phi_s = n_s^\psi/n_h^\psi$.

More recently, Espinosa (2022) builds on these works to monetize welfare gains associated with public policies aimed to improve animal welfare. In this paper, the author uses the number of cortical or pallial neurons as an empirical proxy for utility potentials, as this subset of neurons has been shown to better correlate with cognition than the overall number of neurons. The author also discusses the implications of the choice of the calibration parameter $\psi$ and suggests using $\psi \le 1$. If we assume that a minimal level of sentience can be achieved with a relatively small number of neurons (like recent evidence for insects suggests), we can assume decreasing returns of the number of neurons on utility potentials, leading to $\psi \le 1$. Larger values of $\psi$ are associated with smaller utility potentials for non-human animals. A conservative approach (i.e., an approach that would minimize animal welfare relative to human welfare) would plead to use the largest possible value for $\psi$ (anthropocentrism could be seen as a special case where $\psi \to +\infty$). Altogether, Espinosa suggests that empirical works could use $\psi$ between 0.9 and 1.

Last, we can note that the proxy used to compute utility potentials is aimed to evolve over time with advances in animal and cognitive sciences. In a recent report, Adam Shriver (2022)<fnref n="6" /> notes that neuron counts “roughly track people’s intuitions about the intelligence of different species” and “can provide useful information in cases where we do not have clear intuitions”. However, the raw number of neurons alone does not determine intelligence, and numerous other factors are at play (e.g., firing rate of neurons, number and properties of connections between neurons, spatial density). Shriver also notes that larger animals tend naturally to have more neurons (larger bodies require more neurons) but these neurons might not be involved in the general processing capacity of the brain. Importantly, Shriver underlines that the within-species variance in the number of neurons is small compared to inter-species variance. In our work, we neglect intraspecies variances in the number of neurons and consider equal utility potentials for all members of the same species. Shriver concludes that using the number of neurons as an empirical proxy for utility potential is an improvement compared to the status quo but might be subject to anthropocentric biases about the way we see intelligence and utility potentials.

## 5.4 Quantification of animal welfare

Espinosa and Treich (2023) propose a general framework to quantify animal welfare based on the above elements. In this work, we propose to estimate the utility level *v* of an animal from

<footnote n="6">⁶What neuron counts can and can’t tell us about moral weight, Rethink Priorities, Adam Shriver, 2022.</footnote>
species s using the following master formula:

$$v = \phi_s m \int_{t=0}^{t=T} q(t) dt \qquad (8)$$

The parameter $v$ here corresponds to the monetary equivalent of the lifetime utility of the animal. The function $q(.)$ is the instantaneous welfare level of the animal on a standardized scale where $q = 1$ indicates the highest possible level of welfare and $q = 0$ represents the point where positive and negative experiences cancel each other (i.e., net utility is nil). The net well-being of the animal over its entire life is defined by the integral of instantaneous utility from birth ($t = 0$) to death ($t = T$). The parameter $m$ transforms standardized utility points (i.e., $\phi \times q(.)$) into monetary equivalents.

Figure 4 illustrates this theoretical framework for animal welfare evaluation. It displays the utility of two animals from distinct species over their lifetime. At each moment in time, an animal's utility is equal to $\phi_s \times q(t)$. An animal's highest utility level is therefore equal to $\phi_s$ (because $q(t) = 1$). The animal's utility can take positive and negative values over the lifetime depending on the overall mental state experienced by the animal. The overall lifetime utility, which corresponds to the sum or integral of the instantaneous welfare experienced by the animal over its lifetime is depicted in blue. We call 'utility range' the range of values that the animal's utility can take. The lower bound of the utility function, which is displayed here for the sake of illustration as symmetrical to the upper bound, is equal to $\phi_s \times q_{min}$. The animal represented on the left-hand side of Figure 4 has a lower utility potential than the animal represented on the right-hand side of the Figure. However, because Animal 1 has more positive experiences over its lifetime than Animal 2, it has overall a higher lifetime utility.

The estimation of animal welfare requires defining the instantaneous welfare function $q(.)$, the monetization parameter $m$, and the utility potential $\phi_s$ (we consider here the number of cortical/pallial neurons, as explained before). As a starting point, Espinosa (2022) and Espinosa and Treich (2023) consider the case where animal welfare is estimated through the Five-Freedom framework. In this work, we consider that each of the five freedoms can be violated to different extents (no violation, mild, moderate, severe, very severe violations). We note $W$ the total number of violation points that the animal endures. We consider the following parametric form for $q(.)$:

$$q(t) = \frac{W_0 - W(t)}{W_0} \qquad (9)$$

The variable $W(t)$ corresponds to the number of violation points that the animal endures at date $t$. The parameter $W_0$ corresponds to the threshold value of $W(.)$ where net utility is 0. That is, $W_0$ defines the threshold where life becomes (not) worth living. Conceptually, if the animal has a utility $W_0$ for its entire life, then its life is morally neutral and equivalent to immediate death or nonexistence.

In this model, we set the monetization parameter $m$ as follows. We start by noting that
<figure><img src="image_4.png" /><figcaption>Figure 4: Illustration of the theoretical framework for animal welfare evaluation</figcaption></figure>

going from $q(\cdot) = 1$ to $q(\cdot) = 0$ is equivalent to going from the largest achievable welfare level to having a level equal to zero, which we consider to be equivalent to death (or non-existence). For the calibration, we consider that the unit of time is one day. In case the animal at stake is a human (i.e., $\phi_h = 1$), the welfare loss of losing one year of life with the highest utility level is then equivalent to $365 \times m$ (where 365 is the number of days per year). In economics, the welfare loss associated with losing one year in perfect health is equivalent to losing one unit of QALY. We thus take the economic valuation of one unit of QALY to set the value of $m$. In what follows, we consider then that $m = 402$ Euros.<fnref n="7" /> Note that this assumption undervalues animal welfare. Indeed, losing a point in $q$ is equivalent to losing one day of life with the highest achievable welfare level. However, health is only part of the utility function, such that one point in empirically-estimated QALY does not represent losing one year with the highest achievable welfare but only losing one year in perfect health (which is lower).

We now briefly discuss the comparability and scaling of utilities in this model. The animal

<footnote n="7">⁷The value of $m$ is computed by taking the cost of losing one year of human life equal to 147,000 Euro divided by 365.</footnote>
welfare scores are directly comparable across animal species since we use the same evaluation method based on the Five-Freedom approach for all animals. The scores then translate into utilities through $\phi_s$, so that animal utilities are thus comparable by construction. The comparability with humans' utilities is ensured due to the “high/low scaling” method (Adler 2019; page 190). In our setting, the low scaling point corresponds to the zero-utility level, namely the level of utility equivalent to nonexistence or death for both animals and humans. The high scaling point corresponds to the maximal possible instantaneous welfare, i.e., $q(t) = 1$ for animals and the maximal QALY (=1) for humans. Note finally that both parameters $\phi_s$ and $a_s$ (see equation (1)) determine the importance of a given species in the social objective. However, their interpretations differ significantly. The parameter $a_s$ represents a sort of moral or political weight. If it is equal to one for all species, an equivalent variation in the utility of any two species has the same impact in the social objective. This is in line with the definition of antispeciesism (see section 3). Instead, the parameter $\phi_s$ permits to transform the animal welfare score into utility points for all species. It captures the intensity/complexity of emotions, and is thus naturally related to some physiological proxy.

Before showing an application of this model, let us stress again that the parametric assumption about $q(\cdot)$ only serves as a starting point. More work is needed to discuss the parametrization of $q(\cdot)$. Does a linear function of welfare make sense? Are violation points independent across dimensions? Are we able to capture positive welfare states with the Five-Freedom framework? How to define the lowest bound for $q(\cdot)$?

## 5.5 Challenges in valuing animal welfare

We present here a set of challenges to value animal welfare. First, it is important to recall that we have followed the tradition in economics and chosen a consequentialist/welfarist/utilitarian approach. This choice is of course open to debate, especially given that a large body of research in animal ethics has favored other, e.g., deontological, approaches. A major challenge with alternative approaches would be to relate the analysis to existing economic theory and ultimately obtain quantitative figures as we do here. Nevertheless, we believe that this is an important research direction.

Second, and relatedly, Fleurbaey and Leppanen (2021) emphasize four different approaches to assess animal welfare: the resource-based approach, the hedonistic approach, the objective list approach and the preference-based approach. Here, we have adopted a hybrid approach mixing the hedonistic and objective list approach. Hedonism is sometimes criticized for being too narrow. Happiness might not always be the ultimate goal in life. Another issue is that the hedonistic approach might give priority to the most sensitive individuals, both within and across species. We could end up devoting too many resources to individuals whose happiness is the most reactive to the level of resources (cf. Nozick's utility monsters). Last, hedonism might fall short given the large differences across species.

A third challenge is to evaluate the utility potentials of animals of different species. In previous work, authors have been careful to mention that neurons are only one possible empirical proxy but that, should scientific advances lead to more accurate and widely accessible
proxies, economists should update the proxies used to compute utility potentials. Works in animal consciousness should provide several empirical proxies in the future. For instance, Birch et al. (2020) argue that animal consciousness is multidimensional, and we should then expect empirical proxies on different dimensions. Moreover, various complexities may arise. Note that we cannot exclude that animals with less cognitive capacities suffer more, and not less, in some situations, for instance because they cannot make sense of what happens (think of a dog when thunder rumbles). Relatedly, it is not clear how to compare individuals with very different lengths of life. In our setting, individuals with lower life expectancy count less, other things equal. But perhaps these individuals have a more intense life. In other words, the subjective perception of time may matter.

A fourth challenge concerns the definition of the animal welfare score $q(\cdot)$ across species. The Five-Domain framework provides an important model to evaluate animal welfare but, given that animals differ in the range of emotions they can experience, the definition of $q(\cdot)$ should be different among species. An issue is that defining a welfare function for each single species might be resource-consuming: researchers should first elicit the emotions animals are capable of, and then define an appropriate valuation of $q(\cdot)$ based on this knowledge. However, scientific knowledge about the hedonistic and cognitive capacities of animals is very scarce for some species. A first step could be to evaluate the potential needs and emotions of groups of animals (e.g., mammals, birds, fish).

Fifth, an important question is how to value similar experiences of animals with different utility potentials. For instance, we can reasonably assume that humans and pigs might experience burning pain in a similar way. However, the framework above might not economically value this pain in a similar way. The condition of equal economic valuation of similar experiences between two species of animals is: $\phi_{s(1)}\Delta q_1 = \phi_{s(2)}\Delta q_2$ (with $\Delta q_i$ the change in welfare experienced by individual $i$); the point is that it is not clear why the $\Delta q_i$ should be different across species for a similar pain. A possibility to address this concern could be to have different utility potentials for different experiences: utility potentials could be similar for physical pain or sexual satisfaction for instance but different for other emotional or cognitive experiences.

A sixth and last challenge that we identified concerns uncertainty. As we said above (see Figure 1 for instance), there is still a lot of missing information about the capacities of animals. We believe that it is important to account for this scientific uncertainty. Some have argued for instance that we should apply the precautionary principle regarding which species are sentient (Birch 2017). One might also argue that the threshold at which life becomes worth living is unknown. In fact, our analysis is plagued with uncertainty, both at the level of scientific knowledge regarding animals and that of ethical choices. An economic approach to animal welfare valuation may try to incorporate uncertainty and learning into nonanthropocentric decision making settings.
## 5.6 An application

We now illustrate how to economically value animal welfare changes associated with the implementation of a specific policy. Imagine for instance that French policymakers decide on an intervention to reduce chicken consumption. Let us imagine that they implement a specific policy (such as an increase in chicken price, or a nudge) in canteens and that experts anticipate consumers to substitute on average one chicken meal every two weeks with one meal of legumes. In 2019, the French Ministry of Agriculture indicated that canteens produce about 3.7 billion meals per year in France. Assuming that canteens are open six days a week<fnref n="8" />, about 308 million meals per year containing chicken would be substituted with legumes.

First, we need to compute the number of chickens that would be affected by the policy. Let us consider that a chicken meal contains about 120g of chicken. Assuming that a chicken weighs about 2 kilograms (final weight), the policy would reduce the number of slaughtered chickens by about 18.5 million chickens. Second, we need to estimate the utility $v$ of the average chicken in France.<fnref n="9" /> We consider here the lowest welfare category of chickens as canteens mostly buy these “standard” chickens to save costs. We describe in Espinosa and Treich (2023) the typical living conditions of standard chickens raised in France. The chicken spends on average 38 days at the farm where it mostly suffers from violations of various freedoms (e.g., physical discomfort, pain, and lack of opportunities to express natural behaviors). We estimate that the chicken suffers from about 16 freedom violation points during this stage. The situation worsens during the two last days of its life (transport, slaughter) with 17 freedom violation points for this period.

We consider that the chicken's utility potential is about 0.0035.<fnref n="10" /> Using $m = 402$ (see above), the economic value of the chicken's lifetime welfare is thus given by:

$$v = 402 \times 0.0035 \times \left( \frac{W_0 - 16}{W_0} \times 38 + \frac{W_0 - 17}{W_0} \times 2 \right) \quad (10)$$

The global policy welfare gains are obtained by multiplying the monetary value of the chicken's welfare by the number of chickens that will disappear. Note that the welfare gains depend on the threshold value $W_0$ which defines at which point life becomes not worth living. When $W_0 = 5$, the economic value of the chicken's lifetime welfare is about minus 124 Euros. When $W_0 = 10$, it reduces to minus 34 Euros. In both cases, it is thus estimated that the lives of broilers are not worth living. The overall yearly gains are thus estimated to be about 2.3 billion Euros when $W_0 = 5$, and about 630 million Euros when $W_0 = 10$. Note that despite the relatively mild food policy considered, its monetized benefit for animals is significant.

Alternatively, policy-makers could seek to improve the rearing conditions of the consumed animals. Imagine that, in place of the previous intervention, the policymakers decide to

<footnote n="8">⁸Some canteens are closed during the weekend but some of them still work (hospitals, prisons, etc.) We thus count six full days of work per week.</footnote>

<footnote n="9">⁹We assume that chickens are produced in France, or that they are produced elsewhere with similar living conditions as in France.</footnote>

<footnote n="10">¹⁰Chickens are estimated to have about 85614522 cortical neurons, against 24526423164 for humans. Assuming $\psi = 1$, we have $\phi = 0.0035$.</footnote>
force canteens to buy a significant share of chickens from farms with better animal welfare standards. For instance, French canteens have been forced since 2022 to buy at least 20% of their food from organic farms (Loi Egalim). For the sake of simplicity, let us assume that the policymakers compensate the associated costs such that the consumption of chickens remains stable and that one chicken meal every two weeks now originates from organic farms rather than from “standard” farms. Because organic farms yield better rearing conditions than standard farms, we consider that an organic chicken suffers from 10 violation points for the 81 days it is raised at the farm, and from 17 violation points for the two last days of its life (transport, slaughter). The monetary equivalent of the organic chicken’s lifetime utility is estimated in the same way as the standard chicken above, which yields $v = -121$ with $W_0 = 5$ and $v = -2$ with $W_0 = 10$. The monetized welfare gain of the policy per consumed chicken is thus about 3 Euros with $W_0 = 5$ and 32 Euros with $W_0 = 10$. Note that the replacement gains are relatively small when $W_0 = 5$ because the welfare improvement (10 violation points instead of 17 at the farm) is compensated by the longer farming period (81 days instead of 38). On the contrary, the gains when $W_0 = 10$ are almost as large for this second intervention as for the previous one because $q(t)$ is now equal to 0 at the farm, which is equivalent to non-existence in our total utilitarianism framework. Overall, the gains of this alternative intervention would be about 55.5 million Euros with $W_0 = 5$ and about 592 million Euros with $W_0 = 10$.

This application thus suggests that taking animals seriously into consideration could have a huge economic impact, consistent with early works on the topic (Kuruc and McFadden 2022). In Espinosa and Treich (2023), we calibrate the animal welfare levy as presented in section 4.2. Our calibrations indicate the potential for the levy to escalate to substantial amounts, reaching dozens of Euros per kilogram of meat for animals such as chickens and pigs. In practical terms, these proposed tax rates are anticipated to have the effect of phasing out the most intensive forms of animal agriculture. Moreover, the monetary assessment of externalities on animals significantly outweighs that of environmental externalities (such as climate change, air pollution, and nutrient pollution). Additionally, it goes in an opposing direction compared to the assessment of environmental externalities, as the animal welfare levy on low-polluting meat is usually higher than that on high-polluting meat.<fnref n="11" />

# 6 Optimal species' conservation

We now slightly adapt the theoretical model presented in section 4 to illustrate applications to the conservation of species, for instance the preservation of biodiversity.

In this model, humans derive a benefit from ecosystems. They can conserve some species, at a cost, for instance the forgone production benefits of exploiting a resource that the species rely on. As we will show, if the welfare of some species matters intrinsically, this justifies specific conservation policies. The ideas presented in that section are related to the literature

<footnote n="11">¹¹In fact, the high-polluting cow meat is even subject to a negative tax (i.e., a subsidy) in our setting since the life of standard cows raised in France is estimated to be worth living.</footnote>
on “compassionate conservation” (Ramp and Bekoff 2015; Beausoleil 2020) mentioned earlier.

The social objective is given by:

$$U(n) = b(n) - c(n) + nv \quad (11)$$

where $b(n)$ is the ecosystem benefit and $c(n)$ is the conservation cost. As before, $n$ is the number of individuals in the targeted species.

The FOC for optimal conservation is simply given by:

$$b'(n) + v = c'(n) \quad (12)$$

This optimality condition illustrates that there is a “sentience premium” $v$ on top of anthropocentric conservation considerations. This premium reflects the conservation benefit accruing to sentient species. This premium may for instance lead to prioritizing animal species over plant species.

Using the insights of the previous sections, we know that it is in general socially inefficient to let the management of species’ populations to the market alone. This holds here, even if ecosystem benefits are properly accounted through an optimal environmental policy. The reason is that there is another market failure beyond the environmental externality, namely the externality on sentient species. This justifies a specific policy such as the implementation of a levy that reflects the sentience premium.

We note however that the sentience premium in conservation may not be inconsistent with an anthropocentric approach applied to conservation policies (the indirect approach). Indeed, it has been shown that we, humans, have greater empathy and compassion for the species that are closer to us from an evolutionary perspective, such as other mammals for instance (Miralles et al. 2019). There is also evidence of a “charismatic megafauna” effect (Metrick and Weitzman 1998) in contingent valuation studies. Charismatic megafauna species are large animals such as elephants, gorillas, lions, giant pandas, imperial eagles etc. The point is that these are all sentient species with relatively high cognitive capacities and thus high utility potentials.

It is important to realize that the sentience premium depends on the welfare of individuals in a specific species, not on the total number of individuals in that species. Hence it does not align with common strategies to preserve endangered species which focus on populations, not on individuals. The sentience premium can also be inconsistent with the elimination of invasive species, namely those species which damage ecosystems, i.e., $b'(.) < 0$. Indeed, it would be justified to invest in the conservation of invasive species if the average individual welfare $v$ in that species is high enough. Note that, from a conservation standpoint, invasive species tend to exhibit a strong ecological compatibility with the affected ecosystem, implying potentially significant welfare levels. This highlights the delicate balance between conservation objectives and the impacts on overall well-being.

Following the discussion above, note also that if life is not worth living, i.e. $v < 0$, less, and not more, conservation effort is justified. Some scholars have argued for instance that
r-selected species (i.e., those species with many offspring) may have a negative utility level (Ng 1995, Horta 2010). A large majority of individuals in those species die just after birth, and they usually starve to death or are eaten alive. Arguably, these species do not live a good life on average given that very few individuals live long enough to reproduce. Along this line, Tomasik (2016) even recommends the destruction of some animal habitats for this reason.<fnref n="12" /> Additionally, it is worth noting that the prevalence of r-selected species in the wild underscores the importance of considering the heterogeneity in welfare levels within the same species, along with the equity issues this raises.

Extending the model above, an interesting problem arises when population dynamics is accounted for. In an early innovative work, Clarke and Ng (2006) study non-anthropocentric intertemporal welfare maximization under various assumptions regarding animal population growth. They motivate their study by the culling of kangaroos at the Puckapunyal Army base (Australia). In their section about competing populations, with the help of the well-known Lotka-Volterra model, they show that maximizing offspring is very different from maximizing welfare. Indeed, “welfare could be much higher at lower birthrates without even reducing numbers (at equilibrium)” (Ng and Clarke 2006, p. 420). This analysis suggests that it may be justified for animal welfare reasons alone that humans intervene in nature and design specific animal population control strategies. See also Eichner and Pethig (2006) for a study of fairly general non-anthropocentric setting of nature protection.

Hence, although many biologists, conservation experts, and philosophers have the intuition that we should leave nature alone (in particular because we have no duties toward wild animals), the previous analysis suggests otherwise. This raises the general question of optimal human intervention in the wild. Going one step further, some scholars have even argued that it may be sensible to reduce predation (Cowen 2003; Horta 2010). The argument is that predation generates a lot of suffering, during the death of prey but also because of deterrence (Ripple and Beschta 2004; Clinchy et al. 2013). Using our standard economic approach, predation can be viewed as a negative externality that the predator exerts on the prey and that we may want to reduce. Along this line, Johannsen (2020) suggests that genetic editing such as CRISPR provides a powerful technique to beneficially modify wild animal populations, and in turn reduce suffering in the wild. He argues that it may be optimal for instance to make certain species (such as r-selected species or predators) extinct, change the capacity to suffer of certain animals or change their dietary patterns or reproductive behaviors.

Undoubtedly, the arguments advocating for intervention in conservation efforts are highly contentious. One prominent counter-argument frequently put forward is the concept of human fallibility. The reasoning behind this counter-argument lies in the intricate and interconnected nature of ecosystems, making it exceedingly challenging to predict the full consequences of our actions accurately. In many instances, our interventions fail to yield the desired outcomes and, instead, result in unintended negative repercussions. Historical evidence has repeatedly demonstrated that extensive human intervention in nature can often do more harm than good in the long term. We mention this controversial issue here because it illustrates pretty well

<footnote n="12">¹²See https://reducing-suffering.org/habitat-loss-not-preservation-generally-reduces-wild-animal-suffering/.</footnote>
how complex but also how disturbing might be a non-anthropocentric reflection on conservation issues. We believe however that such a reflection would highly benefit from a greater engagement of environmental and resource economists.

# 7 Concluding words

In this paper, we have argued that we can and should go beyond anthropocentrism in economics. Moreover, we have shown that it is possible to do so without fully abandoning our usual economic methods. However, non-anthropocentric research requires addressing many challenging issues such as the measurement of the welfare of other species, interspecies comparison of welfare, the construction of a multispecies social welfare function, the ethics of animal population or the reduction of wild animal suffering. We are currently in the early stages of this research agenda, but the potential for exploration and discovery appears to be immensely promising.

For sure, our paper on this novel topic is very preliminary, and, hopefully, it will become rapidly out of date due to scientific progress. Our hope is that it contributes to stimulate some scholars in agricultural and resource economics to investigate the topic and indeed make progress. Specific fields devoted to animals already exist in philosophy (i.e., animal ethics) or in law (i.e., animal rights law). We believe that a similar trend should naturally follow in economics. As an encouraging sign perhaps, the Journal of Economic Literature (JEL) classification has just included two new entries: K38: Animal Rights Law; Q18: Animal Welfare Policy.

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