DP2018-22

Revisiting the Impact of Impure
Public Goods on Consumers'
Prosocial Behavior: A Lab
Experiment in Shanghai
Qinxin GUO
Enci WANG
Yongyou NIE
Junyi SHEN

November 5, 2018

Revisiting the impact of impure public goods on consumers’ prosocial behavior:
A lab experiment in Shanghai

Qinxin Guoa, Enci Wangb,*, Yongyou Nieb, Junyi ShencaGraduate School of Economics, Kobe University, Kobe University, 2-1 Rokkodai, Nada, Kobe
657-8501, Japan.
b School of Economics, Shanghai University, 99 Shangda Road, Baoshan 200444, Shanghai,
China
c Research Institute for Economics and Business Administration, Kobe University, 2-1 Rokkodai,
Nada, Kobe 657-8501, Japan.
* Corresponding author. Email: wanencig@gmail.com

Abstract

In this study, we implemented a dictator game experiment to examine how theincrease of the public characteristic in an impure public good affects individuals’
prosocial behavior. A within-subject design was used in the experiment. The dictator
game was repeated six times with an impure public good introduced in four of them.
We observe that the increase of the public characteristic in an impure public good
partly crowds out individuals’ subsequent donations, which could be explained by aseemingly “mental accounting” mental process. In addition, we also find that theselfish behavior of individuals in dictator games with impure public goods, to someextent, has an inertia influence on their subsequent donations when the impure public
good is removed.

Keywords: Impure public goods; Dictator game; Multiple dictators; Mental
accounting

JEL Classification: C91, D64, H41

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1. Introduction
Environmental issues have always been critical problems discussed byenvironmental economists. The externality is known as the basic cause inducing
environmental problems from the perspective of standard economic theory. To
eliminate the externality, “Top-down” governance (e.g., an environment tax) thatrefers to policies and regulations implemented by a government is commonly
regarded as an effective means to deal with environmental issues. However, it might
encounter the risk of rent-seeking (Damania, 1999; Helm, 2010) or harm social
welfare considerably. To avoid this dilemma, green consumption and production,
especially green consumption as a “bottom-up” measure, have become prevalent inrecent years. Instead of compelling consumers to behave environmentally friendly,
green consumption, which involves green products and services, could conveniently
enable us to contribute to the environment. A great deal of previous literature focusedon the factors impacting green consumption through empirical methods (e.g., Laroche
et al., 2001; Albayrak et al., 2012; Panzone et al., 2016; Amatulli et al., 2017).
Nevertheless, they rarely defined green consumption appropriately to describe how
the factors affect the purchase of green products and theorize how green consumption
influences consumers’ behaviors after purchasing green products.
Green consumption could be treated as a means of private provision of a public
good called “impure public good.” Cornes and Sandler (1994) first attempted tomodel characteristic of an impure public good in which they imagined consumers
could acquire joint characteristics–both private characteristic and public characteristic
in one commodity. Applications of this model have been studied in various fields,such as warm-glow giving (Andreoni, 1989; 1990), military alliances (Sandler andMurdoch, 1990), household refuse collection (Dubin and Navarro, 1988), agriculturalresearch (Khanna et al., 1994), pollution abatement (Rübbelke, 2003), andenvironmentally friendly consumption (Kotchen, 2005; 2006). Kotchen (2005; 2006)
followed the steps of Cornes and Sandler whilst improving the model so that it could
explain more issues. Kotchen (2005) separated an impure public good into a2

conventional commodity as well as direct donation and applied comparative statics tocapture how market prices, green production technologies, and social pressure impact
the demand for an impure public good and its public characteristic. Kotchen (2006)
eliminated the numeraire in Kotchen’s (2005) model and demonstrated that according
to heterogeneous preferences and endowments, the impure public good could have
either a beneficial or a detrimental effect on environmental quality and social welfare.
Instead of utilizing the traditional methodology to reveal the relationshipbetween an impure public good and direct donation, Munro and Valente (2016)
implemented a within-subject dictator game experiment, wherein the impure public
good was set as the combination of a private good and a public good. The
counterintuitive result shown in this study was that the impure public good more orless decreased the activity of consumers’ donation in specific green production
technology. This study also found that a self-interested impure public good (i.e., one
whose proportion of private characteristic is larger than that of its public characteristic)
seems able to influence direct donation, whereas an altruistic impure public good doesnot. Munro explained that impure public goods gave individuals an excuse fordecreasing their prosocial behavior without guilt. Engelmann et al. (2017) combined areal product (i.e., a box of chocolates) with a specific amount given to charity torepresent the impure public good and produced results similar to those discussed in
Munro’s paper (Munro and Valente, 2016). The framed impure public good inEngelmann’s paper (Engelmann et al., 2017), to some extent, was a self-interested
impure public good as defined in Munro’s paper (Munro and Valente, 2016) and thereal product-based impure public good seemed to possess the identical characteristicof discouraging consumers’ altruistic behavior. This implies that a self-interested
impure public good needs to be discovered delicately. Nonetheless, both papers
mentioned above fixed an invariant proportion between private characteristic andpublic characteristic for a self-interested impure public good, which suggests thepotential of investigating the influence of changes in the proportions of private andpublic characteristics of the impure public good on individuals’ prosocial behavior.
3

Furthermore, in the aforementioned dictator game experiments, participants
needed to purchase impure public goods with their endowments. This design might
affect the participants’ donation behaviors after purchasing the impure public goods.
The current study aims to eliminate this influence and let participants merely purchasethe private part of the impure public good, with the public part being donated by theexperimenter. Hence the experimenter here could be regarded as another dictator
besides the participants, which forms a multiple dictator game as shown in Dana et al.
(2007). Their experiment demonstrated that the existence of multiple dictators would
incur dictators to become selfish. A bulk of research has proved that behaviors ofparticipants in a multiple dictator game are different from their behaviors in a
traditional dictator game (Dana et al., 2007; Ottone, 2008; Panchanathan et al., 2013).
Dictators in the multiple dictator games made their own decisions and behaved more
selfishly.
In addition, Mazar and Zhong (2010) implemented an experiment comprised
purchasing conventional or green products and a dictator game to confirm theexistence of the aforementioned issue. The results of their experiment were in linewith Munro’s (2016), but Mazar and Zhong suggested that their results were induced
by a “moral licensing effect,” which means that individuals behave lesspro-environmentally after purchasing environmentally friendly products, as if they
have obtained a green license. Momsen and Stoerk (2014) argued that the above
phenomenon might be appropriate to interpret through mental accounting. They
believed green products or services could be divided into two dimensions (i.e.,
consumption needs and ethical benefit), so that individuals will classify them into twomental accounts with distinct shadow prices (Thaler, 1985). Since consumers compare
their choices between conventional and green products through the above twodimensions, their donations in a dictator game might decrease after ethical spending.
In the current study, a within-subject design was implemented in a dictator game
experiment where participants were asked to allocate their endowments between acharity organization and themselves. We aim at investigating whether a multiple4dictator effect and mental accounting exist when impure public goods appear in a
dictator game. Our research makes contributes to previous literature in several way.
First, we replaced the impure public goods in Munro’s design (Munro and Valente,2016) with a real product (i.e., a ball pen) and made an additional donation as part ofthe impure public good to a charity organization, as that in Engelmann et al. (2017).
This change makes the experiment context closer to a real-world situation. Second,
the proportion between private and public characteristics of the impure public good
was designed to vary in the experiment. We attempt to reveal whether this change inproportion will have an impact on participants’ ethical choices. Moreover, it is worth
noting that since the additional donation related to the impure public good wasprovided by the experimenter, every participant was confronted with the same amountof money when they made the allocation between the charity organization andthemselves in each round of the experiment.
The remainder of this paper is organized as follows: The next section describes
elements of the experimental design and implementation. Experimental results anddiscussions are presented in Sections 3 and 4, respectively. The final section offers
conclusions and suggestions for further research.

2. Experimental design and implementation
2.1 Experimental design
To explore the above issues, we applied a within-subject design of dictator
games according to those used by Munro and Valente (2016) and Engelmann et al.
(2017). There were six tasks, including two baseline tasks and four impure public
good tasks in our design. The impure public good was specified as a bundle of a
private good (i.e., a ball pen) and a public good (i.e., an additional donation to acharity organization), which mimics the setting in Engelmann et al. (2017). The
chosen charity organization is Shanghai University Education Development
Foundation (SHUEDF) 1 since it is a charity relevant to the participants in our
1

SHUEDF was established in February 2014 and certified as a charity. This organization receives donations fromeither organizations or individuals for Shanghai University and the donations are applied to set up scholarships,

5experiments. Thus, participants will feel intense benefits if they donate to this charity.
However, in the experiment instructions and during the implementation of theexperiment, we did not use any environmental contents, which was an attempt to
avoid a potential framing effect of green consumption on participants’ choice behavior.
Nevertheless, we could still obtain several general results regarding the impact of
impure public goods from our specific setting.

Table 1. Features of tasks
Task

Order

Endowment

Impure public good

BL1

Round 160 RMBNo

IPG1Round 2

72 RMBYes (self-interested)

Constitution of impure public goodPrivate: a ball pen (12 RMB)
Donation: to SHUEDF (3 RMB)
Private: a ball pen (12 RMB)
IPG2Round 372 RMBYes (self-interested)
Donation: to SHUEDF (6 RMB)
Private: a ball pen (12 RMB)

IPG3Round 472 RMBYes (self-interested)
Donation: to SHUEDF (9 RMB)
Private: a ball pen (12 RMB)

IPG4Round 572 RMBYes (even-interested)
Donation: to SHUEDF (12 RMB)

BL2Round 660 RMBNo

Notes: BL1 and BL2 refer to the two baseline tasks; IPG1, IPG2, IPG3, and IPG4 refer to the four
impure public good tasks.

The summary of the experimental tasks is presented in Table 1. Each participant
was asked to complete six tasks during the experiment; the first and last task (i.e., BL1
and BL2) were baseline tasks (i.e., traditional dictator game without impure public
goods being introduced). In the baseline tasks, each participant was given 60 RMB (1USD≈6.38 RMB) as his/her endowment for this task and was asked to allocate thisamount between himself/herself and SHUEDF; the decision needed to be written on
educational funds, and to support university development, etc. The recipient in the dictator game is set as a charity
in the current design, which follows the design of Eckel and Grossman (1996).

6the recording sheet. The contents of the first and last task were the same. The purpose
for which we included a baseline task at the beginning and one at the end of theexperiments is first to eliminate the possible order effect of the baseline task (Moffatt,2015) and second to examine subjects’ possible behavioral changes after experiencing
the impure public good tasks.
From the second to the fifth task (i.e., IPG1 to IPG4), a specific impure public
good was introduced into each task. The contents of the four impure public good tasks
were similar. In IPG1, each participant received 72 RMB as the endowment and was
asked to purchase a ball pen whose retail price is 12 RMB. When the participants
purchased the ball pen with 12 RMB, 3 RMB out of the 12 RMB would be donated to
SHUEDF by the experimenter. After that, the participants needed to determine how toallocate the remaining 60 RMB (72 RMB subtract 12 RMB) between themselves and
SHUEDF, and the decision needed to be written on the recording sheet. The amountof the donation out of the 12 RMB (i.e., the fixed price of the ball pen in every impure
public good task) in IPG2, IPG3, and IPG4 increased successively; it was 6, 9, and 12
RMB, respectively. 2 In addition, the impure public good in IPG1, IPG2, and IPG3
could be regarded as a self-interested impure public good, since the amount of
donations offered with the impure public good in these tasks was lower than the retailprice of the ball pen. The impure public good in IPG4 was set as an even-interested
impure public good, in which the amount of donation equals the retail price of the ballpen.

2.2 Implementation
Participants were recruited at Shanghai University (SHU) through advertisements
posted on the internet, and 137 students took part in the experiment. The demographic
characteristics of participants are shown in Table 2. Female students account for
57.66% of the sample, and the average age is 22 years. Of the participants, 67.15%
2

There are two reasons for not assigning the amounts of donation out of the 12 RMB in random order. First, we
conducted the experiment in paper-and-pencil style and not via a computer, so perfect randomization was hard toachieved Second, the participants might check or correct their decisions in previous tasks because all the decisions
were written on the same recording sheet; thus, whether the order was random would not be a possible factor
affecting participants’ choices.

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come from a rural area and 59.12% are postgraduate students. In addition, 54.74% of
the participants are students from the School of Economics and most of theparticipants (64.23%) spend 1500 RMB and above for their living expenses per month,excluding dormitory payments. A total of eleven sessions took place in twoclassrooms (one for the experiment and the other for payment) at the School of
Economics, Shanghai University, on May 19th and 20th, 2018.

Table 2. Demographic characteristics of the participants (n=137)
Demographic characteristics% in sample

GenderMale

42.34%

Female57.66%

Age（mean=22）
18-21

36.62%

22-25

61.19%

26 and above

2.19%

Hometown
Urban area

32.85%

Rural area

67.15%

Grade
Undergraduate student

40.88%

Postgraduate student

59.12%

Major in economics?
Yes

54.74%

No

45.26%

Living expenses per month (RMB)
600-999

5.84%

1000-1499

29.93%

1500 and above

64.23%

In each session, we implemented the same six tasks. Each participant received
written experimental instructions (Appendix 1) and a recording sheet (Appendix 2) atthe beginning of the experiment. Before starting the experiment, one experimenter
first read the instructions loudly to assure the participants understood the wholeprocedure. Then, each participant was asked to finish the above-explained six tasks inorder (i.e., from round 1 to round 6) without any communication with other8participants and was informed that their decisions and earnings would remain
anonymous and private. The rewards of each task or round were the amountparticipants left for themselves in that task or round. The participants were asked toraise their hands to hand over their instructions and recording sheets when theyfinished their own tasks and one experimenter would approach them with anautomatic dice machine containing one die. The participants pushed the button on themachine by themselves, and the number shown on the die (any number from 1 to 6)
determined the number of the task or round they could acquire a reward for. When all
the participants in this session finished their tasks as well as rolled the die on themachine, they were asked to answer a questionnaire 3, and then took this questionnaire
to another classroom to receive their rewards. The sessions lasted from 30 to 40
minutes, and the average earnings were 42.6 RMB, which is above the minimum
hourly wage in Shanghai.

3. Results
3.1 Graphical evidence of donation in each task
Figure 1 presents both the voluntary donations and total donations (i.e.,
donations coming from impure public goods plus donations from participants) in thesix tasks. In the baseline tasks (i.e., BL1 and BL2), participants simply needed to makea choice on how to allocate the 60 RMB between themselves and SHUEDF; thus, theparticipants’ voluntary donations equal the total donations, since impure public goods
were not involved in these two tasks. In the impure public good tasks (i.e., IPG1,
IPG2, IPG3, and IPG4), participants were compelled to purchase a symbolical impure
public good consisting of a ball pen at a fixed price of 12 RMB and a donation to
SHUEDF at a varying amount (i.e., 3 RMB, 6 RMB, 9 RMB, and 12 RMB in IPG1,
IPG2, IPG3, and IPG4, respectively) donated by the experimenter. The value of theball pen was then excluded from the endowment of 72 RMB and the participants
could make their own determinations on how to allocate the remaining 60 RMB
3The contents of the questionnaire were about choices for mobile payments. None of questions were relevant to
the purpose of this study.

9between themselves and SHUEDF. Due to this design, the total donations are larger
than the voluntary donations of participants in the tasks with an impure public good.

Figure 1. Voluntary donations and total donations

With respect to the voluntary donations of participants in Figure 1, we first lookat the two baseline tasks. It is observed that the distributions of voluntary donations inthese two tasks are similar. Five out of the 137 participants shared nothing withSHUEDF in BL1 task, whereas 10 out of the 137 participants donated nothing in theBL2 task. Two participants donated all their endowments (i.e., 60 RMB) in both theBL1 and BL2 tasks. About 27% of participants donated 10 RMB out of the 60 RMB in
both the baseline tasks, which accounts for the highest proportion of participants. The
second highest proportion of participants in BL1 and BL2 appears at 30 RMB
10donations, which account for 24.1% and 21.2%, respectively. Nearly 21.9% and17.5% of participants in the BL1 and BL2 tasks, respectively, account for the third
highest proportion of participants, who shared 20 RMB to SHUEDF. We were able todiscover prominent differences in the voluntary donations in the impure public goodtasks and those in the baseline tasks in terms of Figure 1. More participants sharednothing with SHUEDF in the impure public good tasks than in baseline tasks, except
for IPG1 and IPG2, in which the number of zero-contributors in these two tasks isless than that in the BL2 task. The number of full-contributors (i.e., those who donated
60 RMB) in each impure public good task is more than that in the baseline tasks. In
addition, Figure 1 shows that the 10 RMB, 20 RMB, and 30 RMB donations are still
three critical values in the impure public good tasks. The proportions of participants
who donated 10 RMB are 20.4%, 16.8%, 17.5%, and 19.7% in IPG1, IPG2, IPG3,and IPG4, respectively. Participants who donated 20 RMB account for 10.2%, 8.8%,
11.7%, and 13.1% in IPG1, IPG2, IPG3, and IPG4, respectively. With respect to theparticipants who donated half of their endowment after purchasing the impure public
good, the proportions are 12.4%, 10.2%, 6.6%, and 8.0% for IPG1, IPG2, IPG3, andIPG4, respectively.
The details of the participants’ total donations are presented at the bottom of
Figure 1. In the impure public good tasks, none of the total donations are zero becauseof the donations by the experimenter for the impure public goods being added.
Therefore, the least total donations in IPG1, IPG2, IPG3, and IPG4 are 3 RMB, 6
RMB, 9 RMB, and 12 RMB, respectively, and the full donations in these tasks are 63
RMB, 66 RMB, 69 RMB, and 72 RMB, respectively. Comparing this to the voluntary
donation distribution mentioned above, Figure 1 shows that the distribution of total
donations in each impure public good task slightly moves to the right side by theamount of the experimenter’s donation in each task.
The mean of the voluntary donations and total donations in the six tasks areshown in Figure 2. With respect to voluntary donations, the mean in BL1 is higher
than that in BL2 (19.97 versus 18.07 RMB). When comparing to those in the baseline11tasks, the mean donations in the impure public good tasks are almost always lower.
Moreover, the mean voluntary donations seem to decrease as the donations provided
by experimenter in the impure public good tasks increase (i.e., as the publiccharacteristic in the impure public good increases). Nevertheless, the mean total
donations presented in Figure 2 follow the opposite trend, showing a positive relation
with the experimenter’s donations. The reason for this might be that the increase of
the experimenter’s donations does not crowd out participants’ voluntary donations
completely. For instance, the decrease of the mean voluntary donations between IPG1and IPG2 is 1.627 RMB, which is less than the 3 RMB increase in the experimenter’s
donation. The opposite trend in the mean voluntary donation and mean total donation
to some extent probably reflects the participants’ specific mind process when they
make donations. This issue will be further discussed later.

Fig 2. Mean of voluntary donations and total donations

3.2 Regression analysis of voluntary donation and total donation
Table 3 presents the results of two Tobit regressions treating the amount ofvoluntary donation and the amount of total donation as dependent variables. In both12

regressions, we include individual characteristics of participants and the task dummy
variables as independent variables. Of five individual characteristics variables,
Female (i.e., male=0, female=1), Hometown (i.e. urban area=0, rural area=1), andEconomics (not majoring in economics=0, majoring in economics=1) were set as
dummy variables, whereas Age and Living expenses were continuous variables. As
regards the tasks, we defined six dummy variables that equal 1 if participants took
part in the task and 0 otherwise. The dummy variable for the first baseline task (i.e.,BL1) was regarded as the reference of the other five task variables.

Table 3. Tobit regression estimation results
Voluntary donation

Total donation

Constant

47.203(4.19)**

43.417(4.22)**

IPG1-0.951(-1.47)2.217(3.65)**

IPG2-2.677(-4.14)**

3.589(5.91)**

IPG3-3.991(-6.16)**

5.414(8.91)**

IPG4-5.717(-8.75)**7.152(11.75)**BL2-2.049(-3.18)**-1.995(-3.27)**

Female2.234(1.02)

2.418(1.20)

Age-0.378(-0.91)-0.340(-0.89)Hometown

1.531(0.61)

1.516(0.66)

Living expenses-5.386(-2.72)**-4.619(-2.56)*

Economics-4.674(-2.15)*-4.303(-2.17)*Log likelihood-2571.10-2689.54

Sample size

137

137

Notes: ** and * indicate statistical significance at the 1% and 5% levels of confidence, respectively.
Z-statistics are reported in parentheses.

3.2.1 Voluntary donations
As shown in the second column of Table 3, all the estimated parameters of thetask dummy variables except that of IPG1 are statistically significant and havenegative signs, implying that the voluntary donations in the latter four tasks are
significantly less than those in the reference task (i.e., BL1). Furthermore, themagnitudes of IPG1, IPG2, IPG3, and IPG4—although IPG1 is not significant—decrease extras the experimenter’s donations increase. This result is consistent with13

the mean voluntary donation trend shown in Figure 2, which implies participantsprefer to donate less if the impure public good contains more public characteristics(i.e., a higher donation from the experimenter). The statistically insignificant
parameter of IPG1 suggests that the participants may consider IPG1 to be
substantially the same as BL1, possibly because the public characteristic part in thistask is smaller than those in other impure public good tasks. It is unexpected that the
donation in BL2 is significantly less than that in BL1, whereas the smaller parameterin absolute value of BL2 than those of IPG2, IPG3, and IPG4 suggests the donation in
BL2 is still larger than those in these three impure public good tasks. In addition, theincomplete crowding out effect of donations provided by the experimenter, to someextent, could also be captured by these results. For instance, the parameters of IPG2and IPG3 are -2.677 and -3.991, respectively. The difference is 1.314 (=3.991-2.677)
RMB, which means the donation in IPG3 is 1.314 RMB less than that in IPG2. This
amount is less than the increase of 3 RMB in the experimenter’s donation; therefore,
it seems that the increase in the public characteristic of the impure public good does
not completely crowd out participants’ voluntary donations.
With respect to individual characteristics, the parameters of Female, Age, andHometown are statistically insignificant, which indicates these characteristics do notaffect the donation behaviors in our experiment. The parameters of Living expenses
and Economics are both statistically significant and have a negative sign, suggestingthat participants who major in economics or spend more on living expenses per monthwould behave less altruistically and donate less. The result that students majoring ineconomics are inclined to behave less prosocially is consistent with that found in
Marwell and Ames (1981) and Cadsby and Maynes (1998).

3.2.2 Total donations
The results of total donations are presented in the third column of Table 3. All theestimated parameters of the impure public good task variables are statisticallysignificant and have positive signs, implying that the total donations in these tasks are14

significantly higher than that in the IPG1 task. In addition, the magnitudes of IPG1,
IPG2, IPG3, and IPG4 increase as the experimenter’s donations rise, which indeed
shows an adverse trend compared to that in the voluntary donations regression. This
trend exhibits that total donation will increase if the impure public good contains
more public characteristics. In addition, the results of the individual characteristics inthis regression are the same as those in the voluntary donations regression.

4. Discussion
4.1 Multiple dictators
The impure public good tasks of our experiment involved impure public goods
with specific public characteristics. The impure public goods in IPG1, IPG2, and
IPG3 could be treated as self-interested impure public goods, since the amounts
donated by the experimenter are less than the value of the private characteristic (i.e.,the 12 RMB cost of the ball pen), whereas the impure public good in IPG4 could betreated as an even-interested impure public good because the amount donated by theexperimenter is equal to the value of the private characteristic. From the results
described in Section 3, we could deduce that the voluntary donations of participants in
the impure public good tasks will obviously decrease as the experimenter’s donations
increase; in other words, participants will behave less altruistically when they face an
impure public good with more public characteristics, regardless if it is aself-interested or even-interested impure public good. This could possibly beinterpreted through the multiple dictator effect. Our experiment is quite consistent
with the “multiple dictator treatment” implemented in Dana’s paper (Dana et al.,2007). Their experiment demonstrated that the existence of multiple dictators would
incur dictators to become selfish. The experimenter acted like another dictator in our
impure public good tasks, which probably gave the participants an excuse to become
selfish. This is because the final donations received by SHUEDF are the sum of thosefrom both the experimenter and the participants.

15

4.2 Mental accounting
Another interpretation of participants’ voluntary donations showing a negative
correlation with the experimenter’s donations may be that participants set a specificamount for donations to SHUEDF and the experimenter’s donations crowd out theirvoluntary donations. If this is true, the total donations among impure public goodtasks should not be statistically different. However, we find out that total donations
statistically increase along with the experimenter’s donations, but the magnitudes ofthis increase are less than the increase in the experimenter’s donations. We mightinterpret this behavior as a phenomenon of incomplete “mental accounting,” since theparticipants indeed decreased their voluntary donations to allow room for theexperimenter’s donations, as shown in the regression results of voluntary donations.
Participants might treat the two types of donations as one mental account (i.e.,
donations to SHUEDF) instead of separating these two donations into distinct mental
accounts. This implies that the experimenter’s donations might be regarded byparticipants as their own donations to SHUEDF, since it is their purchases of the
impure public goods that induce these donations by the experimenter. This
interpretation is to some extent consistent with that of Momsen and Stoerk (2014).
Nonetheless, this mental accounting is incomplete because participants’ voluntary
donations cannot completely crowd out those by the experimenter. The possible
implication might be that the participants behave slightly more altruistically to offset
the multiple dictator effect, which results in the mental accounting being incomplete.

4.3 BL1 vs. BL2
The donations in BL2 are significantly lower than those in BL1, which indicatesparticipants behave more selfishly after experiencing the impure public good tasks.
For the sake of determining how individuals donated in BL1 and BL2, we have acloser look at the donations in both BL1 and BL2. About 24.8% (34 out of 137)
participants donated less in BL2 than in BL1 and the mean difference of these
donations is 9.32 RMB. Of the 34 participants, 13 donated 5 RMB less in BL2, and 11
16

donated 10 RMB less in BL2. The maximum and minimum difference is 40 RMB and1 RMB, respectively, and 85.3% of the 34 participants’ differences in their donations
between BL1 and BL2 are at least 5 RMB. We check the voluntary donations in thefour impure public good tasks prior to BL2 to seek a reasonable explanation. We findout that 23 out of these 34 participants’ donations decreased continuously, which led
us to suspect that their decreased donations in BL2 might be influenced by theprevious tasks. The selfish behavior seemingly exists as a mental inertia that causes
participants to act less altruistically even when the experimenter’s donations were
excluded in BL2. Nevertheless, the multiple dictator effect vanished in BL2; therefore,
the participants’ voluntary donations were more or less higher in BL2 than those in the
impure public good tasks.

5. Conclusions
In the current study, we applied a within-subject design in the dictator game
experiment in accordance with that in Munro and Valente (2016) and Engelmann et al.
(2017). Our results suggest that a multiple dictator effect was induced by the impure
public good and an incomplete mental accounting effect could be captured throughour experiment. The effect of the impure public good on participants’ prosocial
behavior shown in our study demonstrates the importance of the public characteristic
in the impure public good and suggests that the donations by a third party (e.g., theexperimenter in the current study) might be a vital factor affecting individuals’
voluntary donations.
Moreover, an impure public good is considered as an alternative path toencourage consumers to contribute more to the public good without being
mandatorily required. For instance, green consumption, a prevalent impure public
good, could be utilized to address environmental issues. However, our results offer
evidence that green consumption alone might not be a sustainable measure to induce
consumers to behave more prosocially. Hence, we should be prudent when promoting
impure public goods as an instrument to aid contributions to public goods. Engelmann17

et al. (2017) proposed that making it mandatory for consumers to purchase a green
product would improve contributions to environmental causes. In fact, their research
implied that we need to construct an appropriate institution for the impure public
goods market that could cultivate consumers to behave in alignment with sustaining
prosocial actions. Therefore, producers of impure public goods, as the main
participants in the market, should also be considered in future research on impure
public goods.
Finally, we designed two baseline tasks, one at the beginning and another at theend of the experiment. The results indicate that participants’ behaviors in the impure
public good tasks, which took place between the two baseline tasks, might impact
their behaviors in the second baseline task. Participants became more selfish as theexperimenter’s donation increased, and this trend decreased their donations in the lastbaseline task. This inertia influence should be delicately checked through exploring
how opposite settings related to the impure public good tasks (i.e., the continuous
decrease of the experimenter’s donations) affect participants’ voluntary donations andwhether this influence has an inertia affecting their behaviors when the impure public
good is removed. We leave this issue open and welcome any efforts to further explore
this issue in detail.

Acknowledgements
The financial support from the Japanese Ministry of Education, Culture, Sports,
Science, and Technology through Grants-in-aid for Scientific Research (C) 15K03353
is gratefully acknowledged. All the views expressed in this paper and any errors are
the sole responsibility of the authors.

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Appendix 1: Task instructions
I would like to welcome all the participants in today's experiment. This experiment isdivided into six rounds of tasks. In each round you will be rewarded based on yourdecision, whereas the final reward you receive in the experiment will be determinedby randomly selecting one of these six rounds. The specific selection method will be
explained in detail later. The procedure of the experiment is as follows: First, we
introduce the processes of Rounds 1 to 6, and then you will be asked to do the tasks ofRounds 1 through 6. Remember that you cannot speak to other participants during theexperiment. If this happens, the experiment will be aborted immediately. If you haveany questions, please raise your hand.
We first introduce the process of the Round 1 task.
Instructions for Round 1 task
In Round 1, you will receive 60 RMB. Then, you need to decide how to allocate thesebetween the “Shanghai University Education Development Foundation” (i.e.,
SHUEDF, a non-profit charity established in February 2014, accepting social
donation funds for Shanghai University and utilizing these to support higher
education) and yourself. The amount you leave for yourself will be your reward inthis round.
In addition to the experiment instructions, you also have a “Recording sheet.”
Please look at this sheet. It will be used to record the amount of money you allocate
between SHUEDF and yourself. When you have decided how to distribute the money,
please fill in the amount allocated to the SHUEDF in the “Donate to SHUEDF”
21column in the “Recording sheet” of the Round 1 task; the amount assigned to yourself
should be recorded in the “Assign to yourself” column on the sheet of the Round 1
task.

Instructions for Round 2 task
Round 2 will be conducted after the Round 1. In this task, you will receive 72 RMB.
You have to buy a 12 RMB ball pen we provide you, whereas we will donate 3 RMB
to SHUEDF. Next, you will decide how to allocate the remaining 60 RMB (i.e., 72
RMB minus 12 RMB) between SHUEDF and yourself. The amount you leave foryourself will be your reward in this round.
When you have decided how to distribute the money, please fill in the amountallocated to SHUEDF in the “Donate to the SHUEDF” column in the “Recording
sheet” of the Round 2 task; the amount assigned to yourself should be recorded in the“Assign to yourself” column on the sheet of the Round 2 task.
Instructions for Round 3 task
Round 3 will be conducted after Round 2. In this task, you will receive 72 RMB. You
are asked to buy a 12 RMB ball pen we provide you, whereas we will donate 6 RMB
to SHUEDF. Next, you will decide how to allocate the remaining 60 RMB (i.e., 72
RMB minus 12 RMB) between SHUEDF and yourself. The amount you leave foryourself will be your reward in this round.
When you have decided on how to distribute the money, please fill in the amountallocated to SHUEDF in the “Donate to the SHUEDF” column in the “Recording
sheet” of the Round 3 task; the amount assigned to yourself should be recorded in the“Assign to yourself” column on the sheet of the Round 3 task.

22

Instructions for Round 4 task
Round 4 will be conducted following Round 3. In this task, you will receive 72 RMB.
You have to buy a 12 RMB ball pen we provide you, whereas we will donate 9 RMB
to SHUEDF. Next, you will decide how to allocate the remaining 60 RMB between
SHUEDF and yourself. The amount you leave for yourself will be your reward in thisround.
When you have decided how to distribute the money, please fill in the amountallocated to SHUEDF in the “Donate to the SHUEDF” column in the “Recording
sheet” of the Round 4 task; the amount assigned to yourself should be recorded in the“Assign to yourself” column on the sheet of the Round 4 task.
Instructions for Round 5 task
Round 5 will be conducted after Round 4. In this task, you will receive 72 RMB. You
have to buy a 12 RMB ball pen we provide you, whereas we will donate 12 RMB to
SHUEDF. Next, you will decide how to allocate the remaining 60 RMB (i.e., 72
RMB minus 12 RMB) between SHUEDF and yourself. The amount you leave foryourself will be your reward in this round.
When you have made your decision on how to distribute the money, please fill in theamount allocated to SHUEDF in the “Donate to the SHUEDF” column in the“Recording sheet” of the Round 5 task; the amount assigned to yourself should berecorded in the “Assign to yourself” column on the sheet of the Round 5 task.
Instructions for Round 6 task
Round 6 will be conducted after that of Round 5. In this task, you will receive 60
RMB. Then, you need to decide how to allocate this amount between SHUEDF andyourself. The amount you leave for yourself will be your reward in this round. It

23should be noted that the task of this round is exactly the same as that of the firstround.
When you have decided how to distribute the 60 RMB, please fill in the amountallocated to SHUEDF in the “Donate to the SHUEDF” column in the “Recording
sheet” provided in Round 6 task; the amount assigned to yourself should be recordedin the “Assign to yourself” column on the sheet of the Round 6 task.
The above is the content of the six rounds of today’s experiment. After making
decisions in each round, you can make the next round of decisions on your own
without waiting for our instructions. When all the decisions for the six rounds havebeen completed, and the results have been recorded in the "recording sheet," pleaseraise your hand. We will put an automatic dice machine in front of you, and you needto press the button to roll the dice. The number shown on the die will correspond towhich round you will be paid for, namely, 1 corresponds to the first round, 2 to thesecond round, and so on. For example, if you roll the number 1, you will receive areward based on your decision in the Round 1 task; if the number is 2, you will
receive a reward based on your decision in the Round 2 task, and so on. Furthermore,
if you roll a 2, 3, 4, or 5, you will also receive a ball pen with a market price of 12
RMB. At the same time, we will donate the corresponding amount to SHUEDF. In
addition, when we prepare your reward, please complete a questionnaire for us.

Appendix 2: Recording sheet
Round 1 task
Now that you have received 60 RMB, you can assign it to yourself or donate it to the
Shanghai University Education Development Foundation (i.e., SHUEDF). How will
you divide the amount?

Assign to yourself: ______________ RMB
24

Donate to SHUEDF: _______________RMB

Round 2 task
Now you have received 72 RMB, with 12 of which you must purchase a ball pen we
provide for you. At the same time, we will donate 3 RMB to SHUEDF. Next, you will
decide how to allocate 60 RMB (i.e., RMB 72 minus 12 RMB) between yourself and
SHUEDF. How will you divide the amount?

Assign to yourself: ______________ RMB
Donate to SHUEDF: _______________RMB

Round 3 task
Now you have received 72 RMB, with 12 of which you must purchase a ball pen we
provide for you. At the same time, we will donate 6 RMB to SHUEDF. Next, you will
decide how to allocate 60 RMB (i.e., RMB 72 minus 12 RMB) between yourself and
SHUEDF. How will you divide the amount?

Assign to yourself:______________ RMB
Donate to SHUEDF:_______________RMB

Round 4 task
Now you have received 72 RMB, out of which you must purchase a ball pen costing
12 RMB. At the same time, we will donate 9 RMB to SHUEDF. Next, you will
decide how to allocate the remaining 60 RMB (i.e., RMB 72 minus 12 RMB) between
yourself and SHUEDF. How will you divide the amount?

Assign to yourself:_ _____________ RMB
Donate to SHUEDF: _______________RMB

25

Round 5 task
Now you have received 72 RMB, out of which you must purchase a ball pen costing
12 RMB. At the same time, we will donate 12 RMB to SHUEDF. Next, you will
decide how to allocate the remaining 60 RMB (i.e., RMB 72 minus 12 RMB) between
yourself and SHUEDF. How will you divide the amount?

Assign to yourself:______________ RMB
Donate to SHUEDF:_______________RMB

Round 6 task
Now you have received 60 RMB, you can either assign it to yourself or donate it to
SHUEDF. How will you divide the amount?

Assign to yourself:______________ RMB
Donate to SHUEDF: _______________RMB

26