Social Design Engineering Series

SDES-2020-7

Does Voting Solve Intergenerational Sustainability Dilemma?

Shun Katsuki
School of Economics and Management, Kochi University of Technology

Yoichi Hizen
School of Economics and Management, Kochi University of Technology
Research Institute for Future Design, Kochi University of Technology
30th July, 2020

School of Economics and Management
Research Institute for Future Design
Kochi University of Technology
KUT-SDE working papers are preliminary research documents published by the School of Economics and Management jointly with the ResearchCenter for Social Design Engineering at Kochi University of Technology. To facilitate prompt distribution, they have not been formally reviewed
and edited. They are circulated in order to stimulate discussion and critical comment and may be revised. The views and interpretations expressedin these papers are those of the author(s). It is expected that most working papers will be published in some other form.

Does Voting Solve Intergenerational Sustainability
Dilemma?*Shun Katsuki 1 and Yoichi Hizen 1, 2, 3
1

2

3

School of Economics and Management, Kochi University of Technology, 2-22 Eikokuji-cho, Kochi-shi, Kochi
780-8515, Japan
Research Institute for Future Design, Kochi University of Technology, 2-22 Eikokuji-cho, Kochi-shi, Kochi
780-8515, Japan
Correspondence: hizen.yoichi@kochi-tech.ac.jp

Abstract: Does voting solve intergenerational sustainability dilemma? Do voting rules matter for
inducing people to collectively select a sustainable alternative that leaves more resources for future
generations? To answer these questions, we conduct a laboratory experiment with human subjects
in the framework of intergenerational sustainability dilemma game, in which the own-payoff
maximizing choice by the current generation decreases the size of resource left for the subsequent
generations. The choice is made by voting among the members of each generation, and we compare
three voting rules, ordinary voting, whereby each person has one vote, proxy voting, whereby apart of people are given an extra vote on behalf of the subsequent generations, and two-ballot
voting, whereby all people are given an extra vote. We observe that proxy voting and two-ballot
voting improve the frequency of sustainable choice in comparison with ordinary voting, but thefrequency is still low. This result implies that having people vote individually hardly achieves
sustainable choices by successive generations even if the rules of voting are elaborated to someextent.
Keywords: proxy vote; intergenerational sustainability dilemma; future generation; laboratory
experiment
1. Introduction
Voting is a widely used means of determining policies in modern societies. However, only
people of the current generation can participate in the vote, and future generations, who would be
affected by the outcome of the vote but do not exist yet, cannot participate. The absence of future
generations in voting makes it difficult for intergenerational opinions, especially those that strongly
consider the interest of future generations, to be reflected in voting results. This is the fundamental
issue in creating a sustainable society from a political aspect [1].
The intergenerational issue also exists between elderly and younger people within the current
generation. Children under the legal voting age are not given the right to vote. Furthermore, theproportion of younger people is getting smaller under the aging of population in developed
countries, and hence their opinions are less likely to be reflected in voting outcomes. As a solution tothis problem, giving extra votes to parents with children under the voting age is argued in terms ofintergenerational justice. Van Parijs [2] (p. 309) provides an example of parents’ vote in the French
protectorates of Tunisia and Morocco in the Interwar period: each father of four children or more
was given a second vote. He points out that, although the introduction of parents’ vote is rare, it has
been discussed repeatedly in France from a natalist point of view. Recently, parents’ vote wasdiscussed in the German parliament and envisaged in the draft new constitution of Hungary, but it
was not adopted. Aoki & Vaithianathan [3] conducted an online questionnaire survey to find out*

The authors are grateful to Toshiyuki Himichi, Yoshio Kamijo, Koji Kotani, Kengo Kurosaka, Nobuhiro Mifune,
Yoshitaka Okano, Tatsuyoshi Saijo, and Yuki Yanai for their useful comments. This research was funded by the Japan
Society for the Promotion of Science (KAKENHI): Grant-in-Aid for Scientific Research [C] 17K03769.

1

Japanese voters’ attitudes toward the idea of parents’ vote. The percentages of approval for parents’vote were 68.2% among parents with children under the voting age, 31.5% among parents withchildren over the voting age, and 44.5% among adults without children. Wolf et al. [4] argue thatparents’ vote is justifiable, but its success or failure depends on whether parents use their proxyvotes faithfully to their children's preferences, which must be tested empirically. Kamijo et al. [5]conducted an online experiment in which parents voted to choose an amount of money donatedfrom their endowment to non-profit organizations whose activities were beneficial to future
generations. They observed that females with children under the voting age indicated a larger
amount of donation than others when they were given one vote each, but that this distinction
disappeared when they were given an extra vote on behalf of their children.
Neither children of the current generation nor people of future generations have the right tovote yet, but their fundamental difference is whether to exist currently or not yet. If they exist
currently, we can apply the one-person-one-vote principle to entrust their votes to their parents ortheir legal guardians. Otherwise, we cannot. Wolf et al. [4] (p. 364) state that “voting rights forchildren do not give a voice to the not-yet-born. If a society wants to give the interests of
non-yet-existing individuals their weight too, other tools are needed.” Kamijo et al. [6], Miyake [7],and Kamijo et al. [8] consider an extension of the idea of proxy vote to future generations such thatextra votes are given to a part of people of the current generation with the explanation that they areproxy votes for future generations who cannot join the vote, and hence they are cast on behalf offuture generations. They conduct laboratory experiments to test the effectiveness of such proxyvotes in a framework of one-shot game. In their experiments, participants are divided into groups ofthree, and two of the three are assigned the role of current generation whereas one remaining
participant plays the role of future generation. The two participants of the current generation vote todetermine how to divide an amount of money among the three participants. It is whether to divide it
equally among the three people or to give more to themselves at the expense of future generation’sshare. A proxy vote for the future generation is given to one of the two participants of the current
generation. They observe that proxy voting does not enhance the choice of future-friendly
alternative because proxy votes are not necessarily cast for the future-friendly alternative, andbecause one-ballot voters often switch from the future-friendly alternative to the own-payoff
maximizing alternative if another voter is given an extra vote.
We conduct a similar test but it is in the framework of intergenerational situation where six
generations make successive decisions and the decision by each generation affects the amount of
resource left for the subsequent generations. This intergenerational situation is invented by Kamijo
et al. [9] and called intergenerational sustainability dilemma game (ISDG). The ISDG has been used
to test the effectiveness of various types of face-to-face discussion in solving the dilemma [10-13]. In
the experiment of Kamijo et al. [9], each three-person group (i.e., generation) chose either an
own-payoff maximizing alternative or a sustainable alternative by 10-minute face-to-face discussion.
Group members also determined how to divide the revenue among themselves as a part of theirearnings from their participation in the experiment. Kamijo et al. [9] found that if one of the threemembers in each group was assigned a role of “imaginary future generation,” who was instructed tonegotiate with the other two members on behalf of the subsequent generations, then the frequency ofsustainable choice improved significantly.
In our experiment, we observe that proxy votes improve the frequency of sustainable choice incomparison with the ordinary one-person-one-vote rule, but the frequency is still low. This result
implies that the introduction of proxy votes is not sufficient to achieve sustainability, which isconsistent with the results of the previous literature using the framework of one-shot gameexplained above. Therefore, we need to invent another version of proxy voting, other voting rules, oreven other political institutions. Our result is in contrast to Hauser et al. [14]. In their experiment ofintergenerational goods game, sustainability was achieved with the introduction of voting. We will
discuss about the factors that have possibly generated these different results.

2This paper is organized as follows. Section 2 describes the design of our experiment. Section 3
explains the experimental procedure. Section 4 shows our results. Section 5 discusses about theresults. Section 6 concludes. Appendix A provides the instructions for our experiment.
2. Experimental Design
2.1 Intergenerational Sustainability Dilemma GameWe introduce voting as a way for group members to select an alternative in the intergenerationalsustainability dilemma game (ISDG) invented by Kamijo et al. [9]. Participants are divided into six
groups (i.e., generations) of three members each. They successively choose one of two alternatives, A(own-payoff maximizing choice) and B (sustainable choice). If the first group chooses A, it obtains
3,600 Japanese yen as a group. If it chooses B, it obtains 2,700 yen.
After alternative A is chosen by the first group, the revenue from each alternative for the second
group decreases by 900 yen. That is, the second group obtains 2,700 yen if it chooses A, whereas it
obtains 1,800 yen if it chooses B. On the other hand, after alternative B is chosen by the first group, therevenue from each alternative for the second group is the same as for the first group. Such a reduction
by 900 yen for the next group after choice A is common to all the subsequent groups. That is, if
alternative A keeps being chosen, the revenue from A keeps decreasing from 3,600 yen to 2,700 yen,
1,800 yen, 900 yen, and 0 yen.
2.2 Three Voting Rules
We compare three voting rules. All the voting rules select one of alternatives A and B as thewinner by the majority rule. That is, the alternative that attracts a greater number of votes isdetermined as the group decision among the three members. Ties are broken randomly. For simplicity,
the revenue determined by voting for each group shall be equally divided among the three members.
Abstention is not allowed, and each participant is required to cast each vote for either alternative A or
B.
The only difference among the three voting rules is the number of votes given to each member.
Under ordinary voting, every member has one vote. Under two-ballot voting, every member has two
votes. The instructions explain that the first vote is given as each member’s own vote while the second
vote is given as a proxy vote for the subsequent groups who cannot participate in the vote. Under
proxy voting, only one of the three members has two votes while the other two members have one voteeach. The same explanation about the extra vote as two-ballot voting is given to all the members.
The proxy vote is introduced with the intention of reflecting the interests of future generations
into the current voting results. Hence, for the institution designer, it is ideal that 100% of proxy votes
are cast for sustainable alternative B. However, there is no guarantee that the proxy vote is actuallycast for B because casting it for B does not maximize the payoff for each member of the current
generation.
Proxy voting creates asymmetry in the number of votes among voters. In the case of parents’ vote,it could be justified by the one-person-one-vote principle including children. However, if the proxyvote is on behalf of future generations, that principle does not apply. The two-ballot voting in our
experiment is intended to avoid such asymmetry among voters but reflect the interests of future
generations into the current voting result.
2.3 Group Assignment
As described in Table 1, we had two types of sessions. In ordinary/two-ballot sessions,participants made decisions under ordinary voting and two-ballot voting in random order. In proxysessions, each participant voted in the following two circumstances in random order under proxyvoting: he or she and another member had one vote each while the remaining member had two votes,

3and he or she had two votes while the other two members had one vote each. In both types of sessions,each participant experienced both decisions with one vote and decisions with two votes.
Table 1. Two types of sessions

Session name

Decisions with one vote

Decisions with two votes

Ordinary/two-ballot
Proxy

Ordinary voting
Proxy voting with one voteTwo-ballot voting
Proxy voting with two votes

Note: We had two types of sessions. In ordinary/two-ballot sessions, participants made decisions under ordinary
voting and two-ballot voting in random order. In proxy sessions, they made decisions in two circumstances in
random order under proxy voting, where they were given one vote and where they were given two votes.

Participants were assigned either the ordinary/two-ballot sessions or the proxy sessions according
to the date of their participation. They were also assigned from the first group (i.e., generation) to thesixth group according to the time of their participation. The experiment began with the first group andcontinued through the sixth group. As we see in Appendix A, the instructions differed between the
two types of sessions in terms of voting rules, but were the same among the six groups within eachtype of session. Participants were informed of their own generation on their voting-decision form
distributed after the instructions.
Although participants of the sixth generation received the same instructions as the previous fivegenerations and were given a monetary incentive for their own gratuity determined by their vote, theinstructions did not mention the sixth generation and beyond. They merely mentioned that each groupbelonged to a sequence of groups but did not mention how long the sequence continued. In fact, we
did not have sessions for the seventh generation and beyond.
The participants who gathered at each time in the laboratory were divided into three-member
groups and assigned the same generation. Each group would be connected with other five groups
chosen randomly from the other five generations respectively to form a sequence. In
ordinary/two-ballot (proxy, respectively) sessions, participants of the first group made decisions onwhether to vote for alternative A (3,600 yen) or B (2,700 yen) under ordinary voting and two-ballot
voting (in the two circumstances with one vote or two votes under proxy voting) respectively inrandom order. Experimenters determined randomly which voting rule would be employed (whowould be assigned one vote or two votes among the three members of each group) to calculate
participants’ earnings. We employed a strategy method to collect data from the subsequent groups.
For example, the second group made voting decisions for the possible two cases after the first group
had chosen A and after it had chosen B in random order. The revenue for each group of the second
generation was determined by the group’s choices for the possible two cases under each voting rule(circumstance) and the actual choice of a group selected randomly from the first generation into thesame sequence. Similarly, subsequent groups made voting decisions for all possible cases. That is,under each voting rule (circumstance), there are four cases for the third group, eight cases for the
fourth group, sixteen cases for the fifth group, and thirty-two cases for the sixth group.
3. Experimental Procedures
Participants were recruited from the subject pool of Kochi University of Technology thatconsisted of undergraduate students from various academic disciplines. The total of 156 participants
got together at the social science laboratories in December 2018 and January 2019. Twelve of the 156
were to make sure there was no particular difference between the university’s two campuses.
Therefore, we use the data of 144 participants for our analysis, which consist of 4 groups of 3
participants in each of the 6 generations for each of the 2 types of sessions. Experimenters were also
undergraduate students.
In each session, 12 participants took seats separated from each other by partitions so that they
could not see faces each other but could see the top of heads. Participants drew lots and were divided

4

into four groups of three people each, although they stayed at seats and could not identify who
belonged to the same group as themselves.
Participants read the instructions silently along with an experimenter reading them aloud. As inthe experiment of Kamijo et al. [9], we avoided using words such as generation, sustainability, or any
others that could hint at the purpose of our experiment to the participants. After the instructions, asheet of paper with several quizzes was distributed, and participants answered them to check theircomprehension of the instructions. Then, a voting-decision form was distributed, on which theparticipants’ generation was written. They made voting decisions as explained in Subsection 2.3.
Finally, a questionnaire was distributed, and participants answered questions asking about theirvoting decisions during the experiment as well as their attributes and questions measuring their social
value orientation (SVO) [15]. The SVO questions classify participants into prosocial people and others
according to their answers. Prosocial people are defined as people who are willing to divide anamount of hypothetical resource equally with an anonymous person; prosociality refers to behavior(i.e., to share an amount of resource with others) while altruism refers to motivation. After completingthe questionnaire, participants received the gratuity determined in the voting experiment as well as
900 yen as honorarium for their participation.
This experiment was conducted as a part of voting-experiment project that received an ethicalapproval from the research ethics committee of Kochi University of Technology (code: 35-C1).
Participants participated in the experiment anonymously using their IDs. They simply marked one of
the two alternatives A and B on the paper, and hence there was no physical or psychological influence.
We followed standard procedures in experimental economics.
4. Experimental Results
4.1 Voting Outcomes
We compare the three voting rules with respect to the frequency of sustainable choice B. Since
participants in our experiment were randomly divided into three-person groups without identifying
their group members, the actual voting result of each group (i.e., A or B) was merely one of thevarious possibilities. For example, suppose that six participants of a generation voted for alternatives
A, A, A, A, B, and B respectively under ordinary voting when they faced a particular choice historyof the previous generations. If one group were formed with three participants who chose A, A, andA while another group were formed with the remaining three participants who chose A, B, and B,
then the decisions made by the two groups would be A and B. On the other hand, if the six
participants were divided into participants with A, A, and B and participants with A, A, and B, thenthe group decisions would be A and A. To take such randomness of group-level observations into
account, we conduct, after the experiment, the following four-step computer simulation regarding
the group formation by using the data on each participant’s choice for each possible choice history of
the previous generations under each voting rule.
Step 1: From the first generation of 12 participants, the computer selects 3 participants randomly
to form a group. Under proxy voting, the computer also determines randomly who is given two
votes. The computer determines the group’s decision (i.e., A or B) using the data on the 3participants’ actual decisions collected in the experiment. If alternatives A and B are in a tie, thecomputer selects one of them randomly.
Step 2: For the second generation of 12 participants, the computer performs the same groupformation as in step 1. The computer determines the group’s decision (i.e., A or B) using the data on
the 3 participants’ actual decisions made after the group decision of the first generation determinedin step 1.
Step 3: The computer repeats the same procedure as in step 2 until the sixth generation. Then thecomputer obtains the number of times alternative B is selected in the sequence of six generations.

5

Step 4: The computer repeats the above three steps 50,000,000 times for each voting rule. Then thecomputer obtains 50,000,000 sequences of group decisions made by six generations for each voting
rule.
Table 2 shows the results of the computer simulation based on the actual decisions made by theparticipants in our experiment. The rows represent the number of times alternative B is selected as agroup decision in a sequence of six generations, whereas the columns represent voting rules. For
example, “0” in the cell of row “6” and column “Ordinary” indicates that, according to our data,
there never happens that all the six generations choose alternative B under ordinary voting even if
50,000,000 sequences of six generations are randomly created. The distributions of the number oftimes alternative B is selected among six generations are different between any two of the threevoting rules at the 1% level of statistical significance by the Kolmogorov-Smirnov test.
Table 2. Simulation results of the number of times alternative B is selected among six generations

Voting rule65
Number of times
alternative B isselected amongsix generations

4
3
2
1
0

Sum

OrdinaryTwo-ballot

Proxy

0
(0.000%)5,974(0.012%)90,390(0.181%)
474,954(0.950%)4,329,254(8.659%)17,267,664(34.535%)
27,831,764(55.664%)
50,000,000(100.000%)

22,969(0.046%)
289,459(0.579%)1,822,002(3.644%)
3,312,781(6.626%)
10,234,731(20.470%)
12,062,625(24.125%)
22,255,433(44.511%)50,000,000(100.000%)

15,920(0.032%)
166,605(0.333%)640,143(1.280%)2,892,368(5.785%)8,468,484(16.937%)
14,866,201(29.732%)
22,950,279(45.901%)
50,000,000(100.000%)

Note: For example, “0” in the cell of row “6” and column “Ordinary” indicates that, according to the data fromour experiment, there never happens that alternative B is selected six times among six generations underordinary voting even if 50,000,000 sequences of six generations are randomly created.

Under ordinary voting, more than half of the sequences of six generations end up choosing
alternative A all the time. Choosing alternative B once or less occupies more than 90%. Two-ballot
voting and proxy voting improve the frequency of choice B to a statistically significant degree, but
the successive selection of B is still far from being achieved. Kamijo et al. [9] employed face-to-face
discussion as a way for group decision, and observed that the frequency of choice B improved from
28% to 60% if one of the three group members played the role of the representative for thesubsequent generations. Their percentages are calculated as the percentage of groups that havechosen B among all groups of their five generations. If we calculate the same measure from Table 2,
the percentages are 9.25%, 17.11%, and 14.66% under ordinary, two-ballot, and proxy voting,respectively. Voting does not seem appropriate for achieving sustainability in the ISDG even if
proxy votes are introduced.

6

4.2 How to Use Each Vote
Next, we investigate how to use each type of vote under each voting rule. Table 3 shows thepercentage of choice B made with each type of vote by all participants of each generation for all
possible cases of choice histories of previous generations under each voting rule. For example, thevalue “33.33“ in the upper left cell means that 33.33% of the individual decisions made by the 12
participants of the first generation under ordinary voting was to vote for alternative B while theremaining 66.67% was for alternative A. At the aggregate level, we can see over the six generations
that, under proxy voting, the use of their own vote when participants are given two votes is more orless similar to the use of the vote when they are given one vote. This tendency is also found between
the use of their own vote under two-ballot voting and the use of the vote under ordinary voting. On
the other hand, although the frequency of proxy votes being cast for alternative B is far from 100%,
which is the ideal level intended by the institution designer, and stays around 50%, it is higher thanthat of own votes in every generation under both two-ballot voting and proxy voting. Theseobservations imply that the presence of proxy vote is the main factor for the difference in thefrequency of choice B as a group decision among the three voting rules (Table 2). In fact, proxyvotes occupy 0%, 50%, and 25% of all votes given to participants under ordinary voting, two-ballot
voting, and proxy voting, respectively.
Table 3. Percentage of choice B by vote type and by generation (%)

SessionVotingNumbernameruleof votes

Ordinary

Ordinary

One

/two

Two

-ballot-ballot

Two
One

Proxy

Proxy

Two

Generation

Vote type

1st

2nd

3rd

4th

5th

6th

Unspecified

33.33

20.83

4.17

30.21

12.50

29.43

Own

25.00

16.67

10.42

37.50

17.19

33.07

Proxy

58.33

45.83

20.83

53.12

63.02

48.96

Unspecified

16.67

16.67

43.75

17.71

30.73

7.81

Own

16.67

16.67

35.42

16.67

37.50

6.77

Proxy

25.00

62.50

50.00

54.17

40.10

50.00

Note: The percentage in each cell is calculated from the decision-making data of the 12 participants assigned tothat cell for all the possible cases of choice histories of the previous generations.

4.3 Regression Analysis with Individual Data
Finally, we conduct a logistic regression analysis to identify the factors that induce choice B at
the individual level. We divide our data by vote type, and run a regression for each data set. We
have three types of votes as in Table 3, (i) unspecified votes given to each participant underordinary voting and two of the three group members under proxy voting, (ii) own votes, and (iii)proxy votes, both of which are given to each participant under two-ballot voting and one of thethree group members under proxy voting. We do not include the first generation because it has noprevious generations in contrast to the other generations. The number of observations for eachgeneration is the number of cases in the choice history of the previous generations (i.e., 2, 4, 8, 16,
and 32 cases for the second to the sixth generations) times the number of participants for each typeof vote (i.e., 24 subjects for every generation). The total of 1,488 observations are available for the
regression of each type of vote.
The dependent variable is whether to vote for alternative B (1) or A (0). Explanatory variablesconsist of whether the vote was made under proxy voting (1) or the other two voting rules (0) (i.e.,
proxy dummy), the proportion (between 0 and 1) that alternative B was selected in previous
generations (i.e., proportion of choice B), whether the participant is prosocial (1) or not (0) according
to the SVO measure (i.e., prosocial dummy), whether the participant is female (1) or not (0) (i.e., female
dummy), and dummy variables for each generation where the second generation is the baseline. In

7order to confirm whether the effects of the proportion of choice B and each participant’s prosociality
differ depending on generations, their interaction terms with generation dummies are also included.
The random effect for each participant is introduced in the regressions to take into account the factthat a set of data are generated from each participant.
The proxy dummy is intended to examine the effect of asymmetry in the number of votes
among group members. The proportion of choice B is intended to examine the effect of thedecisions made by the previous generations on the decision of the current generation. The prosocial
dummy and the female dummy are intended to examine the effect of each participant’s
characteristics on his or her decision. Although the effects of proxy dummy and female dummy are
difficult to predict, the proportion of choice B and the prosocial dummy are expected to havepositive effects on the probability of alternative B being chosen by each participant in voting.
Table 4 shows the estimation results of the random-effect logistic regressions. As predicted, theprosocial dummy has a positive and statistically significant effect on the probability of voting for B
for every type of vote. The SVO measures prosociality towards an anonymous person who exists
currently. This estimation result suggests that such prosociality could be also activated in a situationof successive group decisions.
Table 4. Estimation results of the random-effect logistic regressions

Unspecified voteOwn vote

Proxy vote

Explanatory Variables

Coef.

Std. err.

Coef.

Std. err.

Coef.

Std. err.

Proxy dummy

0.423

0.845

-0.1970.892-0.321

0.957

Proportion of choice B

0.772

1.263

4.729**

2.267-0.0001.013% of choice B × 3rd gener. dum.

2.584

1.835

-2.195

2.553

0.601

1.498

% of choice B × 4th gener. dum.

2.419

1.698

-1.0522.523

3.042**

1.452% of choice B × 5th gener. dum.

1.564

1.524

-2.1152.416

3.233**

1.267% of choice B × 6th gener. dum.

3.110**

1.424-1.5142.346

2.428**

1.143

Prosocial dummy

5.725**

2.495

7.875***

2.868

7.246**

2.974

Prosocial dum. × 3rd gener. dum.

-0.2803.222-3.9583.485-1.5103.549

Prosocial dum. × 4th gener. dum.

-3.6492.991-5.081

3.370-4.9493.562

Prosocial dum. × 5th gener. dum.

-2.1962.940-4.246

3.290-6.178*3.520

Prosocial dum. × 6th gener. dum.

-2.011

2.946-4.176

3.325-8.097**

3.590

Female dummy

0.994

0.862

0.984

0.906

-0.8540.991

3rd generation dummy-1.671

2.506

3.580

3.139

-3.880*

2.035

4th generation dummy

0.433

2.184

4.099

3.066

-1.5752.074

5th generation dummy-0.538

2.144

3.689

3.010

-1.130

2.032

6th generation dummy-1.268

2.000

2.858

2.932

0.149

1.883

Constant-6.763***1.880-10.600***

2.862-0.563

1.562

Number of Observations

1,488

1,488

1,488

Wald χ2

71.72***

67.39***

63.21***

Notes: The dependent variable is whether to vote for B (1) or A (0). The statistical significance at the 10%, 5%,
and 1% levels are denoted by *, **, and ***, respectively.

8However, the coefficients of interaction terms between prosocial dummy and generation
dummies are negative for every type of vote. In particular, for proxy vote, they are statisticallysignificant for the fifth and sixth generations, and their negative effects offset the positive effect ofthe prosocial dummy. On the other hand, for proxy vote, the proportion of choice B has significantly
positive effects for the fourth generation and later. These observations imply that, for decision
making on proxy vote, as the generations go forward, the influence of prosociality diminishes while
how often sustainable choices have been made in the previous generations becomes important. The
importance of the frequency of sustainable choice in the previous generations is also found for thesixth generation in the regression of unspecified vote. For own vote, the proportion of choice B has
a positive and statistically significant effect while its interaction terms with generation dummies are
not statistically significant.
The larger proportion of choice B by the previous generations can have the following threeeffects on the decision of the current generation. First, it might induce indirect reciprocity:
participants might think that they should leave a larger pie for the subsequent generations because
their previous generations did so for their generation. Second, it might have an income effect: since
the larger proportion of choice B by the previous generations leaves a larger pie for the current
generation, the current generation can earn a sufficiently large reward even if it chooses alternative
B. Finally, it might form a custom: the larger proportion of choice B by the previous generations
might form a custom of choosing B, and the current generation might merely follow the custom
which the previous generations had followed. All these three effects work to enhance choice B. Ourcurrent society could be regarded to have been choosing the own-payoff maximizing alternative A
successively. Our experimental result suggests that such successive own-payoff maximization leads
to a higher frequency of own-payoff maximization by the subsequent generations.
Our results regarding the positive effects of the proportion of sustainable choice by theprevious generations and each individual’s prosociality on the probability of voting for thesustainable alternative are consistent with those of Shahen et al. [16]. They conducted an ISDG
experiment with each generation being represented by one person, and observed that the larger
proportion of unsustainable choice by previous generations led to a higher frequency ofunsustainable choice by the current generation, and that prosocial participants were more likely tochoose the sustainable alternative.
5. Discussion
Our result is in contrast to the observation of Hauser et al. [14] that the introduction of voting
increases the frequency of sustainable choice dramatically in their intergenerational goods game
(IGG). We think that the ISDG represents a more difficult situation for sustainability than their IGG
as explained below.
In the IGG, each generation consists of five members, and each member extracts any number ofunits between 0 and 20 from a common pool of 100 units endowed to his or her generation. If thetotal number of units extracted by the five members does not exceed a predetermined threshold (50,40, or 30 units), the size of common pool recovers to 100 units for the next generation. If it exceeds
the threshold, the common pool is destroyed so that nothing is left for the next generation, whichmeans the end of the game. In this setting, participants with any social preference would want toavoid the catastrophic outcome. They seem to be most satisfied if they achieve both the extraction of
the common pool up to the threshold and the full recovery of the common pool for the next
generation. In fact, Hauser et al. [14] observed in most five-person groups that a majority ofmembers extracted 10 units or less, but that a minority extracted a larger number of units and hence
the total number of units exceeded the threshold.
In the IGG with median voting, on the other hand, the number of units each member extracts is
common to the five members of each generation and determined by voting among the fivemembers. Each member votes for a number of units, and the median among the five proposals
determines the number of units each member extracts. Under such median voting, Hauser et al. [14]9observed that the total number of units extracted by each generation fell within the threshold withan extremely high frequency. Since a majority extracted 10 units or less in the IGG, the median
member should also vote for 10 units or less in the IGG with median voting. Voting is a device toreflect the preference of majority, and works well to prevent a minority from acting against the
majority. Therefore, if the sustainable sequence of generations is preferred by a majority, it isachieved through voting.
In the ISDG, on the other hand, only two alternatives are available, the own-payoff maximizing
alternative and the sustainable alternative. Even if participants want to increase their payoff by asmall amount, there is no alternative between the two; they need to choose the own-payoff
maximizing alternative. Furthermore, choosing it does not end the game; it merely decreases thecommon pool left for the next generation by 900 yen. Therefore, participants in the ISDG seem to begiven a stronger incentive to choose the own-payoff maximizing alternative than in the IGG. In fact,a majority of our participants preferred the own-payoff maximizing alternative under ordinary
voting. Two-ballot voting and proxy voting increased the sustainable choice, but it was to a small
extent.
6. Conclusions
In this paper, we conducted a laboratory experiment with human subjects to examine thepossibility of proxy vote on behalf of future generations improving the frequency of sustainablechoice in the intergenerational sustainability dilemma game (ISDG). We observed that the ordinary
one-person-one-vote rule resulted in a very low frequency of sustainable choice, and that the
introduction of proxy votes enhanced the sustainable choice, but it did so only slightly. Our negative
result for voting in achieving sustainability is in contrast to the positive result of Hauser et al. [14].
Our discussion about the difference in game structure between the ISDG and their intergenerational
goods game (IGG) suggests that the ISDG represents a more difficult situation for sustainability thanthe IGG. A majority prefers the own-payoff maximizing alternative in the ISDG whereas a majority
prefers a sustainable choice in the IGG. In principle, voting is a means for collective decision-making
that reflects the preference of a majority.
The key to sustainability issues from the perspective of majoritarianism is that while themajority of the current generation and beyond, including future generations, prefers sustainableoptions even if they are costly for the current generation, the majority of the current generation
does not. Therefore, for sustainable options to be chosen in today’s society, it is necessary to either
include future generations in the current decision-making process or change the preferences of the
majority of the current generation in a direction that is compatible with future generations. The
proxy vote we examined in this paper is intended to include future generations in the vote.
However, since it is people of the current generation who cast proxy votes, their preferences need tobe compatible with future generations for the proxy vote to succeed in selecting sustainable options.
It is hoped that the introduction of proxy votes would direct voters’ attention to the interest of
future generations and result in the selection of sustainable options, but our experiment has shownthat the proxy vote does not have a sufficiently large effect in the ISDG. As a future task, we mustcome up with a political institution that does not overly rely on, or rather brings out, theprosociality of the current generation towards future generations.
One of the things that could be thought of as activating prosociality towards future generations
is to give the context of sustainability. In our experiment, we used words such as subsequentgroups instead of future generations. However, if the proxy vote is introduced in the actual voting
system of our society, it must be explained as the proxy vote for future generations instead ofsubsequent groups. It is another future task to examine the effect of the context of sustainability on
current people’s decisions regarding intergenerational issues.

10Appendix A
This appendix provides an English translation of the Japanese instructions used in our
experiment. The “attached table” in the instructions is Figure 1 of Kamijo et al. [9] with grid lines
added.
Instructions(1) Outline of the experiment
As an honorarium for participation in this experiment, 900 yen will be paid to each participant.
We will pay this off after this experiment is over. Additional gratuities will be determined by the
choice explained below.
In this experiment, participants in the laboratory will be randomly divided into groups of three.
You will not be told who the other members of your group are.
Each group chooses between A and B. Depending on that choice, the gain will be determined.
Please see the attached table. The numbers in this table are in hundreds. For example, 27 is 2,700 yen.
If the first group chooses A, it gains 3,600 yen. If it chooses B, it gains 2,700 yen. Each group’s choice
will be decided by voting. The additional gratuity you receive will be the amount of the gain chosen
by your group divided equally by all the three members.
The figure below shows an overview of the experiment. Your group will be connected to othergroups that are formed at other times. For example, suppose that your group is the third group in asequence of groups. Then, the gains from A and B for your group will change in response to the
choices made at the previous times by the first and second groups of the sequence to which yourgroup belongs. Note that there will be no effect of the previous groups for the first group because itis the first group in its sequence. Depending on the choice of your group, the gains from A and B for
the subsequent groups of your sequence will change.
Groups assembled at the same time in the laboratory will be given the same order in different
sequences. Hence, the choices of other groups gathering in this laboratory now do not affect the
choice of your group. It is the choices of the previous groups in the same sequence that will influence
your group’s choice. The choice of your group will also affect the choices of the subsequent groups
in the same sequence.
Sequence

...
1st
2nd
group
group
(3 people)

4th
group

3rd
group

5th
...
group

(2) How gains are determined
The gain for each group is determined as follows. If the first group chooses A, the gain for thesecond group will be reduced by 900 yen for both A and B. In other words, like the shaded part of
the following table, the second group gains 2,700 yen from A and 1,800 yen from B. On the other
hand, if the first group chooses B, the second group faces the same choice as the first group. In otherwords, the second group gains 3,600 yen from A and 2,700 yen from B.
1st groupAB

2nd groupA

2,700 yenB

1,800 yenA

3,600 yenB

2,700 yen

3,600 yen

2,700 yen11

Next, let us consider the third group. Now, suppose that the first group has chosen A. Then, thesecond group faces the choice in the shaded part of the table above. The table below shows the gains
for the third group that follow the shaded part of the table above. Here, if the second group chooses
A, the gain from A for the third group decreases by 900 yen and becomes 1,800 yen, and the gainfrom B also decreases by 900 yen and becomes 900 yen. On the other hand, if the second groupchooses B, the third group gains 2,700 yen from A and 1,800 yen from B.
2nd groupAB

3rd groupA

1,800 yenB

900 yenA

2,700 yenB

1,800 yen

2,700 yen

1,800 yen

As explained so far, if one group chooses A, the gain for the next group will be reduced by 900
yen for both A and B. On the other hand, if one group chooses B, the gains for the next group will be
the same as the previous ones for both A and B.
Please refer carefully to the attached table. Raise your hand if you have any doubts. Then an
experimenter will come to your assistance. During the experiment, conversations with others except
experimenters are strictly prohibited.
(3) Decision-making by each group
You will be given a sheet of paper after the instructions, on which the gains from A and B for
your group are written. These gains are determined by the choices of the previous groups althoughthose for the first group are known to be 3,600 yen from A and 2,700 yen from B. If the gain will be
negative as a result of your group’s choice, you must pay it from your honorarium for participationin this experiment, 900 yen.
You will make voting decisions for two different experiments.
●Experiment X[The following paragraph is presented in ordinary/two-ballot sessions.]
In Experiment X, all members of your group have one vote each. Group members are respectively asked tocast their votes for A or B. The alternative that receives the more votes will be the decision of your group.
[The following two paragraphs are presented in proxy sessions.]
In Experiment X, one of the three members of your group, except you, has two votes, while you and theremaining member have one vote each.
You and the remaining member are respectively asked to cast your votes for A or B. The member who has
two votes is asked to cast one vote as “his or her vote” and another vote as a “proxy vote on behalf of thesubsequent groups” who cannot participate in your group’s vote. He or she is free to decide whether to cast eachof the two votes for A or B. The alternative that receives the more votes will be the decision of your group. If a tie
happens, a lottery will determine which of the two alternatives is chosen.
As explained so far, the gains from A and B for your group will change depending on the
choices by the groups who participated in this experiment before you. There are multiple possiblecombinations for the choices of the previous groups. You will make voting decisions on all the casesthat can arise.
For example, suppose that your group is the third group. Then, there are four possible cases forthe choices of the previous groups, “the first group chose A and the second group chose A,” “thefirst group chose A and the second group chose B,” “the first group chose B and the second group12

chose A,” and “the first group chose B and the second group chose B.” Hence, the third group will
make voting decisions on a total of four cases. Similarly, the number of cases on which voting
decisions are made is one for the first group, two for the second group, eight for the fourth group,
sixteen for the fifth group, and so on.
●Experiment Y[The following two paragraphs are presented in ordinary/two-ballot sessions.]
In Experiment Y, all members of your group have two votes each. The other rules are the same as
Experiment X.
You are asked to cast one vote as “your vote” and another vote as a “proxy vote on behalf of the subsequentgroups” who cannot participate in your group’s vote. You are free to decide whether to cast each of the two votes
for A or B. The alternative that receives the more votes will be the decision of your group. If a tie happens, alottery will determine which of the two alternatives is chosen.
[The following two paragraphs are presented in proxy sessions.]
In Experiment Y, out of the three members of your group, you have two votes while the other two members
have one vote each.
You are asked to cast one vote as “your vote” and another vote as a “proxy vote on behalf of the subsequentgroups” who cannot participate in your group’s vote. You are free to decide whether to cast each of the two votes
for A or B. The other two members are respectively asked to cast their votes for A or B. The alternative thatreceives the more votes will be the decision of your group. If a tie happens, a lottery will determine which of thetwo alternatives is chosen.
As in Experiment X, you will be asked to make voting decisions on all the cases that can arise.
When you make voting decisions, the two experiments are listed in random order. In otherwords, some participants make voting decisions in the order of “Experiment X → Experiment Y,”
while the other participants make voting decisions in the order of “Experiment Y → Experiment X.”
You will find out where in a sequence of groups your group has been placed (i.e., first, second,and so on) on the form of paper handed out after the instructions.
(4) How to determine additional gratuities
Your additional gratuities will be determined in accordance with the following procedures.
[The following two steps are presented in ordinary/two-ballot sessions.][1] Either Experiment X or Experiment Y is randomly selected.
[2] The case that your group has faced is determined based on "the actual choices of the previous groups" in theselected experiment.
[The following two steps are presented in proxy sessions.][1] Out of the three members of your group, two members are assigned to Experiment X while one member isassigned to Experiment Y randomly.
[2] The case that your group has faced is determined based on "the actual choices of the previous groups."[3] The votes of all the group members in that case will be counted, and the choice of your group isdetermined.
[4] The resulting gain is divided into three equal parts, and each part is given to each of your groupmembers.
(5) Questionnaire
Once you have completed your voting decisions on all cases, you will receive a questionnaire froman experimenter and answer it.

13

References
1.

2.
3.

4.
5.
6.
7.

8.
9.
10.

11.
12.
13.

14.
15.

16.

Saijo, T. Future Design. In The Future of Economic Design: The Continuing Development of a Field as Envisioned
by Its Researchers; Laslier, J.-F., Moulin, H., Sanver, M.R., Zwicker, W.S., Eds.; Springer: Berlin/Heidelberg,
Germany, 2019, 253-260.
Van Parijs, P. The Disfranchisement of the Elderly, and Other Attempts to Secure Intergenerational Justice.
Philosophy & Public Affairs 1998, 27(4), 292–333.
Aoki, R.; Vaithianathan, R. Sedaikan no Seiji Keizai: Senkyo ni kansuru Ankēto Chōsa kara
(Intergenerational Political Economy: From a Questionnaire Survey on Elections). In Japanese, Discussion
Paper No. 540, Center for Intergenerational Studies, Institute of Economic Research, Hitotsubashi
University, 2009.
Wolf, S.; Goldschmidt, N.; Petersen, T. Votes on Behalf of Children: A Legitimate Way of Giving Them a
Voice in Politics? Constitutional Political Economy 2015, 26(3), 356-374.
Kamijo, Y.; Tamura, T.; Hizen, Y. Effect of Proxy Voting for Children under the Voting Age on Parental
Altruism towards Future Generations. Futures 2020, 122, 102569.
Kamijo, Y.; Hizen, Y.; Saijo, T. Hearing the Voice of Future Generations: A Laboratory Experiment of“Demeny Voting.” Discussion Paper SDES-2015-8, Kochi University of Technology, 2015.
Miyake, K. Jikken kara Saguru Domein Tōhyō Hōshiki no Yūkōsei to sono Kadai (The Effectiveness andChallenges of Demeny Voting System Explored from an Experiment). In Japanese, Graduation Thesis,
School of Management, Kochi University of Technology, 2015.
Kamijo, Y.; Hizen, Y.; Saijo, T.; Tamura, T. Voting on Behalf of a Future Generation: A Laboratory
Experiment. Sustainability 2019, 11, 4271.
Kamijo, Y.; Komiya, A.; Mifune, N.; Saijo, T. Negotiating with the Future: Incorporating Imaginary Future
Generations into Negotiations. Sustainability Science 2017, 12, 409-420.
Nakagawa, Y.; Kotani, K.; Kamijo, Y.; Saijo, T. Solving Intergenerational Sustainability Dilemma throughImaginary Future Generations: A Qualitative-Deliberative Approach. Discussion Paper SDES-2016-14,
Kochi University of Technology, 2016.
Shahrier, S.; Kotani, K.; Saijo, T. Intergenerational Sustainability Dilemma and the Degree of Capitalism inSocieties: A Field Experiment. Sustainability Science 2017, 12, 957-967.
Shahrier, S.; Kotani, K.; Saijo, T. Intergenerational Sustainability Dilemma and a Potential Solution: Future
Ahead and Back Mechanism. Discussion Paper SDES-2017-9, Kochi University of Technology, 2017.
Timilsina, R.R.; Kotani, K.; Nakagawa, Y.; Saijo, T. Concerns for Future Generations in Societies: A
Deliberative Analysis on Intergenerational Sustainability Dilemma. Discussion Paper SDES-2018-16,
Kochi University of Technology, 2018.
Hauser, O.P.; Rand, D.G.; Peysakhovich, A.; Nowak, M.A. Cooperating with the Future. Nature 2014, 511,
220-223.
Van Lange, P.A.M.; De Bruin, E.M.N.; Otten, W.; Joireman, J.A. Development of Prosocial, Individualistic,
and Competitive Orientations: Theory and Preliminary Evidence. Journal of Personality and Social Psychology
1997, 73(4), 733-746.
Shahen, M.E.; Kotani, K.; Saijo, T. How Do Individuals Behave in the Intergenerational Sustainability
Dilemma? A Strategy Method Experiment. Discussion Paper SDES-2020-1, Kochi University ofTechnology, 2020.

14