sustainability
ArticleDoes Voting Solve the Intergenerational
Sustainability Dilemma?
Shun Katsuki 1 and Yoichi Hizen 1,2, *1
2*School of Economics and Management, Kochi University of Technology, 2-22 Eikokuji-cho, Kochi-shi,
Kochi 780-8515, Japan; shun.katsuki.715@gmail.com
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

Received: 30 June 2020; Accepted: 3 August 2020; Published: 5 August 2020


Abstract: Does voting solve the intergenerational sustainability dilemma? Do voting rules matter
when trying to induce people to collectively select a sustainable alternative that leaves more resources
for future generations? To answer these questions, we conducted a laboratory experiment using anintergenerational sustainability dilemma game in which players are asked to choose between twoalternatives. Choosing the alternative that maximizes the players’ immediate benefit decreases theresources left for subsequent generations. The choice is made by the votes cast within small groups
representing successive generations. We compare three voting rules: ordinary voting, whereby each
person in the group has one vote; proxy voting, whereby some but not all of the players are given an
extra vote to cast on behalf of subsequent generations; and two-ballot voting, whereby all players are
given an extra vote. We observe that both proxy voting and two-ballot voting increase the frequency
at which the sustainable alternative is selected; however, the frequency of such a choice remains low.
This suggests that voting individually is a relatively ineffective way to elicit sustainable choices fromsuccessive generations even if the rules of voting are modified.
Keywords: proxy vote; intergenerational sustainability dilemma; future generation; laboratory
experiment

1. Introduction
Voting is a widely used means of determining policies in modern societies. Clearly, however,
only members of the current generation can participate in the vote despite the fact that subsequent
generations can be greatly affected by the outcome. The absence of future generations in voting
makes it difficult for intergenerational opinions, especially those that prioritize the interests of future
generations, to be reflected in voting results. From a political perspective, this is a fundamental issue
in creating a sustainable society [1].
A somewhat similar intergenerational issue exists between the young and the elderly within
the current generation. Children under the legal voting age are excluded from the voting process.
Moreover, as the proportion of young people continues to decline in developed countries, their opinions
will be even less likely to be reflected in voting outcomes in the future. As one solution to this problem,
giving extra votes to parents with children under the voting age has been proposed as a way to promoteintergenerational justice. Van Parijs [2] (p. 309) cites as an example the voting system in the French
protectorates of Tunisia and Morocco during the Interwar period, where the fathers of four or morechildren were given a second vote. He points out that, although the introduction of this type of parents’vote is rare, it has been discussed repeatedly in France from a natalist point of view. Recently, a parents’vote was discussed in the German parliament and was envisaged in a draft of the new constitution
Sustainability 2020, 12, 6311; doi:10.3390/su12166311

www.mdpi.com/journal/sustainability

Sustainability 2020, 12, 6311

2 of 14in Hungary (where it failed to be adopted). Aoki & Vaithianathan [3] conducted an online survey todetermine the attitude of Japanese voters toward the idea of a parents’ vote, reporting approval ratingsof 68.2% among parents with children under the voting age, 31.5% among parents with children overthe voting age, and 44.5% among adults without children. Wolf et al. [4] argued that a parents’ vote isjustifiable, but that its success or failure depends on whether parents use their proxy votes faithfully toreflect their children’s preferences, a proposition that needs to be tested empirically. Kamijo et al. [5]conducted an online experiment in which parents voted to choose an amount to be donated fromtheir endowment to non-profit organizations whose activities were beneficial to future generations.
The authors observed that females with children under the voting age voted for a larger donation thanothers when they were each given one vote, but that this difference disappeared when they were given
an extra vote to be cast on behalf of their children.
There is, of course, a fundamental difference between the case of children currently living with theirfamilies and yet-to-be-born members of future generations: For the children of the current generation,
we can readily apply the one-person-one-vote principle to entrust their votes to their parents or legal
guardians, while for the unknown and uncountable members of future generations, such a simple
prescription is hardly possible. Wolf et al. [4] (p. 364) state that “voting rights for children do notgive 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] considered
an extension of the idea of proxy voting to future generations by giving extra votes to a subset ofmembers of the current generation, along with the explanation that these extra votes were to serve as
proxy votes for future generations unable to participate in the current voting process. To examine theeffectiveness of such a system, the authors conducted a laboratory experiment involving a one-shotgame in which participants were divided into groups of three, with two of the group members assigned
the role of the current generation and the remaining member taking the role of future generations.
The two current-generation participants were to vote to determine how to divide a given amount ofmoney among the three participants. The choice was whether to divide the money equally among thethree group members or to give more to themselves at the expense of the future generation’s share.
A proxy vote for the future generations was given to one of the two current-generation participants.
The study found that such proxy voting did not promote the choice of a future-friendly alternative,
as the proxy votes were not necessarily cast for the future-friendly alternative and the one-ballot votersoften switched from the future-friendly alternative to the own-payoff maximizing alternative whenanother voter is given an extra vote.
We conduct a similar test here, but in this case, the experiment involves an intergenerationalsituation in which small groups representing six successive generations are asked to make decisions
that significantly affect the number of resources left for subsequent generations. This intergenerationalsituation, presented in the form of a game called the intergenerational sustainability dilemma game
(ISDG), was first proposed by Kamijo et al. [9] and has been used to test the effectiveness of various
types of face-to-face discussions for solving the dilemma that the game poses [10–13]. In the experimentconducted by Kamijo et al. [9], each three-person group (i.e., generation) chooses either an own-payoff
maximizing alternative or a sustainable alternative after engaging in a ten-minute face-to-face discussion.
Group members also determine how to divide the revenue that they earn as a group from their choice.
Kamijo et al. [9] found that if one of the three members in each group was assigned the role of“imaginary future generation” and was instructed to negotiate with the other two members on behalfof the subsequent generations, the frequency of sustainable choice improved significantly.
In our current experiment, while we observed that the proxy vote improved the frequency ofthe sustainable choice in comparison with the conventional one-person-one-vote rule, the frequencyof such a choice was still low. This suggests that the introduction of proxy votes is not sufficient toachieve sustainability, which is consistent with the result reported for the one-shot game describedabove. What appears to be needed, then, is another version of proxy voting, other voting rules,
or even other political institutions. It should be noted that our result is in contrast to Hauser et al. [14],Sustainability 2020, 12, 6311

3 of 14

who reported that in their experiment involving an intergenerational goods game, sustainability wasachieved with the introduction of median voting. We will later discuss the factors that may account forthese different results.
The remainder of this paper is organized as follows: Section 2 describes the design of theexperiment; Section 3 explains the experimental procedure; Section 4 gives the results; Section 5
presents a discussion of results; Section 6 offers conclusions and suggests future directions. Appendix A
provides the instructions given to participants in the experiment.
2. Experimental Design
2.1. Intergenerational Sustainability Dilemma Game
In this experiment, the intergenerational sustainability dilemma game (ISDG) proposed by
Kamijo et al. [9] was used to introduce voting as a way for group members to choose one of twoalternatives. The participants are divided into six groups (i.e., generations) of three members each, andthe groups successively choose one of two alternatives: Alternative A, the own-payoff maximizing
choice, or Alternative B, the sustainability-oriented choice.
According to the game’s rules, if the first group chooses alternative A, the group receives a total of3600 Japanese yen. If the group chooses alternative B, it receives only 2700 yen. The choice then passes
to the second group. If alternative A was chosen by the first group, the payoff from each of the twoalternatives for the second group decreases by 900 yen. That is, the second group will receive 2700
yen if it chooses alternative A or 1800 yen if it chooses alternative B. On the other hand, if alternative
B was chosen by the first group, the possible payoffs for the second group will be the same as they
were for the first group (i.e., 3600 yen and 2700 yen, respectively). The 900-yen reduction applies toeach subsequent group whenever the preceding group has chosen alternative A. Thus, if alternative A
is chosen each time, the payoff from A decreases from 3600 yen to 2700 yen, to 1800 yen, to 900 yen,and to 0 yen.
2.2. Three Voting Rules
We compare three voting rules. All three rules select the winning alternative according to themajority vote in the group. That is, the alternative that attracts the greater number of votes is considered
the group’s choice. Ties are broken randomly. For simplicity, the payoff determined by the group’s
vote will be equally divided among the group’s three members. Abstention is not allowed, and thevote(s) of each participant must be cast for either alternative A or alternative B.
The only difference among the three voting rules is the number of votes given to each groupmember. Under ordinary voting, each group member has only one vote. Under two-ballot voting, eachmember is given two votes. In this case, the group members are told that the first vote is the member’s
own vote and that the second vote is a proxy vote for subsequent groups who will be making choices
later in the game. Under proxy voting, only one of the three members of the group is given two votes,
while the other two members have just one vote each to cast. The same explanation regarding the extra
vote as that given in the two-ballot voting case is given here.
The proxy vote is introduced as a way of injecting the interests of future generations into the current
voting process. Hence, for the institution designer, the ideal result would be that 100% of the proxyvotes are cast for sustainable alternative B. However, there is no guarantee that a proxy vote will actually
be cast for B since this would reduce the payoff for each member of the current-generation group.
Proxy voting creates an asymmetry in the number of votes allotted to voters. In the case of theparents’ vote, the asymmetry can be justified under the traditional one-person-one-vote principle,
which, in this case, would include children. However, if a proxy vote is to be cast on behalf offuture generations, applying the same principle is clearly problematic. The two-ballot voting scheme
included in our experiment is intended to avoid such asymmetry but still reflect the interests of future
generations in the current voting process.

Sustainability 2020, 12, 6311

4 of 142.3. Group Assignment
As described in Table 1, two types of sessions were conducted in our experiment: ordinary/twoballot sessions and proxy sessions. In the ordinary/two-ballot sessions, the participants made theirvoting choices under ordinary voting and two-ballot voting in random order. In the proxy sessions,each participant voted in each of two circumstances in random order: He/she was one of the two
members with one vote each while the remaining member had two votes, or he/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

Ordinary voting

Two-ballot voting

Proxy

Proxy voting with one vote

Proxy voting with two votes

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

Participants were assigned to either the ordinary/two-ballot sessions or the proxy sessions
according to the date of their participation. They were also assigned to a generational group (groups 1
through 6) according to the time of their participation. The experiment began with the first group andcontinued through the sixth group. As shown 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 each typeof session. Participants were informed of their assigned generation (group) on their voting-decision
form, which was distributed after the instructions were given.
Although participants in the sixth-generation groups received the same instructions as the previous
five generations and were given a monetary incentive in the form of a gratuity determined by theirvote, their instructions did not mention the sixth generation and beyond. While they were told thateach group belonged to a sequence of groups, no mention was made of how far the sequence extended.
In actuality, we did not have sessions for the seventh generation or beyond.
The participants who gathered at each of the various times in the laboratory were divided into
three-member groups and assigned to the same generation. Each group was to be connected withfive other groups chosen randomly from the other five generations to form a sequence. At the end oftheordinary/two-ballot sessions, one of the two voting rules was randomly selected, and participants’earnings were calculated based on the decisions made under that rule. Similarly, in the proxy sessions,one of the two circumstances was randomly selected for each participant under the condition that only
one of the three members would be given two votes in each group.
We employed a strategy method to collect data from the subsequent groups for each voting ruleor circumstance. For example, the second group made their voting decisions for two cases—(1) after
the first group had chosen A and (2) after the first group had chosen B—in random order. The payofffor each second-generation group was determined by the actual choice made by a randomly selectedgroup of the first generation and the second group’s choice for that case. Similarly, subsequent groups
made voting decisions for all possible combinations of choices made by the groups that preceded them.
Thus, under each voting rule or circumstance, there were four cases to be considered by the thirdgroup, eight cases by the fourth group, sixteen cases by the fifth group, and thirty-two cases by thesixth group.
3. Experimental Procedures
Participants were recruited from the subject pool of Kochi University of Technology and consistedof undergraduate students from various academic disciplines. A total of 156 participants assembled
at the social science laboratories in December 2018 and January 2019. Twelve of the 156 participants

Sustainability 2020, 12, 6311

5 of 14were used to ensure that there were no significant differences between the university’s two campuses.
The data for 144 participants were used in the final analysis. Four groups of three participants in eachof the six generations were formed for each of the two types of sessions. The experimenters were also
undergraduate students.
In each session, 12 participants took seats separated from each other by partitions so that they
could not see the faces of the others but could see the tops of their heads. The participants drew lots
and were divided into three-person groups. Irrespective of the group, all participants remained intheir original seats and could not identify who belonged to their group.
The participants read the instructions silently while an experimenter read them aloud. As in theexperiment reported by Kamijo et al. [9], we avoided using words such as generation, sustainability,
or any others that could hint at the purpose of the experiment. In order to check the participants’comprehension of the instructions, each participant was asked to answer several quiz questions on a
written form distributed after the instructions were given. They were then given a voting-decision
form on which the participant’s generation was written. At this point, the participants proceeded tomake their voting decisions as explained in Section 2.3. When the voting finished, a questionnaire
was distributed and the participants answered questions about their voting decisions as well as
questions focused on participant attributes and questions measuring their social value orientation(SVO) [15]. The SVO questions were used to classify participants as either “prosocial” or “other.”
Prosocial people were defined as those willing to divide an amount of a hypothetical resource equallywith an anonymous person; in general, prosociality refers to behavior that is intended to benefit
others. (This differs from altruism which refers to one of the possible motivations for such behavior.)
After completing the questionnaire, the participants received the gratuity determined in the voting
experiment as well as 900 yen as an honorarium for their participation.
The experiment was conducted as part of a voting-experiment project approved by the research
ethics committee of Kochi University of Technology (code: 35-C1). Participants who took part in theexperiment did so anonymously, using their IDs. In choosing alternatives, each participant simply
placed a mark on the voting form to indicate their choice of either A or B. There was no physical or
psychological influence. The standard procedures of experimental economics were followed.
4. Experimental Results
4.1. Voting Outcomes
We compared the three voting rules with respect to the frequency of sustainable choice B. Since theparticipants in the experiment were randomly divided into three-person groups without identifying
their other group members, the actual voting result for each group (i.e., A or B) was merely one of thevarious possibilities. To illustrate, suppose six participants from a particular generation voted A, A, A,
A, B, and B, respectively, under ordinary voting when faced with a particular choice history of previous
generations. If one group was formed with three participants who chose A, A, and A while anothergroup was formed with the three remaining participants, who chose A, B, and B, then the decisions
made by the two groups would be A and B, respectively. On the other hand, if the six participants
were divided into groups consisting of a group of three participants who chose A, A, and B and asecond group of three participants who chose A, A, and B, then the group decisions would be A and A.
To take such randomness of group-level observations into account, we conducted, after the experiment,
the following four-step computer simulation regarding group formation by using the data on eachparticipant’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 toform 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 threeparticipants’ actual decisions collected in the experiment. If alternatives A and B are in a tie,
the computer selects one of them randomly.

Sustainability 2020, 12, 6311

6 of 14

Step 2: For the second generation of 12 participants, the computer performs the same group formation
as in step 1. The computer determines the group’s decision (i.e., A or B) using the data on
the three participants’ actual decisions made after the group decision of the first generation
determined in 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.
Step 4: The computer repeats the above three steps 50,000,000 times for each voting rule. In this way,
the computer obtains 50,000,000 sequences of group decisions made by six generations foreach voting rule.
Table 2 shows the results of the computer simulation based on the actual decisions made by theparticipants in the experiment. The rows represent the number of times alternative B is selected asa group decision in a sequence of six generations, whereas the columns represent the voting rules.
For example, the cell entry of “0” in row “6” and column “Ordinary” indicates that, according to ourdata, there were no cases in which all six generations choose alternative B under ordinary voting evenwhen 50,000,000 sequences of six generations were randomly created. The distribution of the numberof times alternative B is selected among six generations differs between any two of the three voting
rules at the 1% level of statistical significance using the Kolmogorov-Smirnov test.
Table 2. Simulation results for the number of times alternative B is selected among six generations.
Voting Rule

Number of times
alternative B is selectedamong six generations

Sum

Ordinary

Two-Ballot

Proxy

6

0
(0.000%)22,969(0.046%)15,920(0.032%)55974(0.012%)

289,459(0.579%)166,605(0.333%)

4

90,390(0.181%)

1,822,002(3.644%)640,143(1.280%)3474,954(0.950%)3,312,781(6.626%)2,892,368(5.785%)2

4,329,254(8.659%)10,234,731(20.470%)

8,468,484(16.937%)

1

17,267,664(34.535%)

12,062,625(24.125%)

14,866,201(29.732%)

027,831,764(55.664%)

22,255,433(44.511%)22,950,279(45.901%)

50,000,000(100.000%)

50,000,000(100.000%)

50,000,000(100.000%)

Note: For example, the “0” in the “6” row and “Ordinary” column indicates that, according to the data from ourexperiment, there were no cases in which alternative B is selected six times among the six generations under ordinary
voting, even when 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 every time. Indeed, choosing alternative B one or fewer times occurs more than 90% of thetime. 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] employedface-to-face discussion as a way to influence group decisions and observed that the frequency of choice
B improved from 28% to 60% if one of the three group members played the role of representativeof the subsequent generations. The percentages were calculated as the percentage of groups thatchose B among all groups in their five generations. If we calculate the same measure from Table 2,
the percentages are, respectively, 9.25%, 17.11%, and 14.66% under ordinary, two-ballot, and proxySustainability 2020, 12, 6311

7 of 14voting. Based on these results, even if proxy votes are introduced, voting does not appear to achievesustainability in the ISDG.
4.2. How to Use Each Vote
Next, we investigated each type of vote under each voting rule. Table 3 shows the percentage ofchoice B made with each type of vote by all participants of each generation for all possible cases ofchoice histories of previous generations under each voting rule. For example, the value “33.33“ inthe upper-left cell indicates that 33.33% of the individual decisions made by the 12 participants ofthe first generation under ordinary voting were a vote for alternative B, while the remaining 66.67%
were for alternative A. At the aggregate level, we can see over the six generations, under proxy voting,the use of the participants’ own vote when they are given two votes is more or less similar to theiruse of their vote when they are given one vote. This tendency is also found between the use of theirown vote under two-ballot voting and their 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 remains around 50%, it is higher than that of the own
votes in every generation under both two-ballot voting and proxy voting. These observations suggestthat the presence of a proxy vote is the main factor accounting for the difference in the frequency ofchoice B as a group decision among the three voting rules (Table 2). In fact, proxy votes constitute,respectively, 0%, 50%, and 25% of all votes given to participants under ordinary voting, two-ballot
voting, and proxy voting.
Table 3. Percentage of choice B by vote type and by generation (%).
SessionName
Ordinary/two-ballot

Voting Rule

Number of
Votes

Vote Type

Ordinary

One

Unspecified

Two -ballot

Two
One

Proxy

Proxy
Two

Generation
1st

2nd

3rd

4th

5th

6th

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 for the 12 participants assigned to thatcell for all the possible cases of choice histories of the previous generations.

4.3. Logistic Regression Analysis with Individual Data
Finally, we conducted a logistic regression analysis to identify the factors that appear to induce
choice B at the individual level. We divided our data by vote type and performed a regression foreach data set. There were three types of votes, as indicated in Table 3: (1) unspecified votes given
to each participant under ordinary voting and two of the three group members under proxy voting,(2) own votes, and (3) proxy votes, both of which are given to each participant under two-ballot
voting, and to only one of the three group members under proxy voting. We do not include the first
generation because, in contrast to the other generations, it has no previous generations. The number ofobservations for each generation 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, respectively) times the number ofparticipants for each type of vote (i.e., 24 participants for every generation). In all, 1488 observations
were available for the regression involving each type of vote.
The binary dependent variable indicated a vote for either alternative B (1) or A (0). The set of
explanatory variables represented the following factors: whether the vote was made under proxyvoting (1) or the other two voting rules (0) (i.e., proxy dummy), the proportion (between 0 and 1) oftimes that alternative B was selected in previous generations (i.e., proportion of choice B), whether theSustainability 2020, 12, 6311

8 of 14

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,with the second generation as the baseline. In order to confirm whether the effects of the proportionof choice B and each participant’s prosociality differed depending on generation, terms for theirinteraction with the generation dummies were also included. The random effect for each participant
was introduced in the regressions to take into account the fact that a set of data was generated fromeach participant.
The proxy dummy was used to examine the effect of asymmetry in the number of votes amonggroup members. The proportion of choice B was used to determine the effect of the decisions madeby previous generations on the decision of the current generation. The prosocial dummy and thefemale dummy were used to reveal the effect of each participant’s characteristics on his or her
decision. Although the effects of the proxy dummy and the female dummy were difficult to predict,the proportion of choice B and the prosocial dummy were expected to have positive effects on theprobability of alternative B being chosen by each participant in the voting.
Table 4 shows the estimation results of the random effect logistic regressions. As predicted,
the prosocial dummy had a positive and statistically significant effect on the probability of voting for B
for every type of vote. The SVO here measures the individual’s prosociality towards an anonymous
person who exists currently. This estimation result suggests that such prosociality can be activated in asituation involving successive group decisions.
Table 4. Estimation results for the random-effect logistic regressions.
Unspecified Vote

Own Vote

Proxy Vote

Explanatory Variables

Coef.

Std. Err.

Coef.

Std. Err.

Coef.

Std. Err.

Proxy dummy
Proportion of choice B% of choice B × 3rd gener. dum.
% of choice B × 4th gener. dum.
% of choice B × 5th gener. dum.
% of choice B × 6th gener. dum.
Prosocial dummy
Prosocial dum. × 3rd gener. dum.
Prosocial dum. × 4th gener. dum.
Prosocial dum. × 5th gener. dum.
Prosocial dum. × 6th gener. dum.
Female dummy
3rd generation dummy
4th generation dummy
5th generation dummy
6th generation dummy

0.423
0.772
2.584
2.419
1.564
3.110 **
5.725 **
−0.280−3.649−2.196−2.0110.994−1.6710.433−0.538−1.268−6.763
***

0.845
1.263
1.835
1.698
1.524
1.424
2.495
3.222
2.991
2.940
2.946
0.862
2.506
2.184
2.144
2.000

−0.1974.729 **
−2.195−1.052−2.115−1.5147.875 ***
−3.958−5.081−4.246−4.176
0.984
3.580
4.099
3.689
2.858
−10.600
***

0.892
2.267
2.553
2.523
2.416
2.346
2.868
3.485
3.370
3.290
3.325
0.906
3.139
3.066
3.010
2.932

−0.321−0.0000.601
3.042 **
3.233 **
2.428 **
7.246 **
−1.510−4.949−6.178 *−8.097 **−0.854−3.880 *−1.575−1.130
0.149

0.957
1.013
1.498
1.452
1.267
1.143
2.974
3.549
3.562
3.520
3.590
0.991
2.035
2.074
2.032
1.883

2.862

−0.5631.562

Constant
Number of observations
Wald χ2

1.880

1488
71.72 ***

1488
67.39 ***

1488
63.21 ***

Note: The dependent variable indicates whether the vote of an individual is for B (1) or A (0). Statistical significanceat the 10%, 5%, and 1% levels is denoted by *, **, and ***, respectively.

On the other hand, the coefficients for the interaction terms between the prosocial dummy andthe generation dummies were negative for every type of vote. In particular, for the proxy vote,they were statistically significant for the fifth and sixth generations, with negative effects that offset
the positive effect of the prosocial dummy. However, for the proxy vote, the proportion of choice B
had significantly positive effects for the fourth generation and later. These observations imply that,for decision making on the 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 the sixth generation in the regression of the unspecified vote. For own vote, the proportion of

Sustainability 2020, 12, 6311

9 of 14

choice B had a positive and statistically significant effect, while its interaction terms with the generation
dummies were not statistically significant.
The larger proportion of choice B by previous generations could affect the decision of the current
generation in one or more of the following three ways: First, it might induce indirect reciprocity—that
is, the participants might believe that they should leave a larger pie for subsequent generations because
previous generations had done so for them. Second, it might have an income effect—meaning that since
the larger proportion of choice B by previous generations left a larger pie for the current generation,
the current generation is able to earn a sufficiently large reward even if it chooses alternative B.
Finally, it might create a custom—that is, the larger proportion of choice B by previous generations
could be perceived by the current generation as an established custom to be followed. All threeeffects would work to encourage the selection of choice B. On the other hand, our society could be
regarded as one that has successively and consistently chosen the own-payoff maximizing alternative
A. Our experimental result suggests that such successive own-payoff maximization leads to a higher
frequency of own-payoff maximization by subsequent generations.
Our study’s results regarding the positive effects of the proportion of sustainable choices by
previous generations and each individual’s prosociality on the probability of voting for the sustainable
alternative are consistent with those of Shahen et al. [16], who conducted an ISDG experiment
wherein each generation was represented by one person. They observed that a larger proportion ofunsustainable choices made by previous generations led to a higher frequency of the unsustainablechoice by the current generation, and that prosocial participants were more likely to choose thesustainable alternative.
5. Discussion
Our results are in contrast to those of Hauser et al. [14], who observed in their intergenerational
goods game (IGG) that the introduction of voting increases the frequency of sustainable choicedramatically. By way of explanation, we believe that the ISDG represents a more difficult situation forsustainability than is the case in the IGG.
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 the total
number of units extracted by the five members does not exceed a predetermined threshold (50, 40,
or 30 units), the size of the common pool reverts to 100 units for the next generation. However, if
the number of extracted units exceeds the threshold, the common pool is destroyed so that nothingis left for the next generation, which means the end of the game. In this setting, participants having
any social preference would want to avoid a catastrophic outcome. It would be reasonable to expectthat such players would be most satisfied by extracting from the common pool an amount up to thethreshold, thus ensuring the full recovery of the common pool for the next generation. In fact, Hauser
et al. [14] observed that, in most of the five-person groups, a majority of members 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, the number of units that each member extracts are common to all
five members of each generation and is determined by voting among the five members. Each member
votes for a number of units and the median of the five proposals is used as the number of units thateach member extracts. Hauser et al. [14] observed that under such median voting the total number ofunits extracted by each generation was below the threshold with an extremely high frequency. Since in
the IGG a majority extracted 10 units or less, it follows that the median member would also votefor 10 units or less in the IGG with median voting. As voting is a device to reflect the preference ofthe majority, it works well to prevent a minority from acting against the majority. Therefore, if thesustainable sequence of generations is preferred by the majority, it will be accomplished through voting.
In the ISDG, on the other hand, only two alternatives are available—the own-payoff maximizing
alternative and the sustainable alternative. If participants want to increase their payoff by even aSustainability 2020, 12, 6311

10 of 14

small amount, there is no intermediate alternative available to them; they would need to choose theown-payoff maximizing alternative. Furthermore, choosing the own-payoff maximizing alternative
does not end the game; it merely decreases the common pool left for the next generation by 900
yen. Hence, participants in the ISDG seem to be given a stronger incentive to choose the own-payoff
maximizing alternative than is the case in the IGG. In fact, a majority of our participants preferred theown-payoff maximizing alternative under ordinary voting. While two-ballot voting and proxy voting
increased the selection of sustainable choice, the increase was quite small.
6. Conclusions
In this paper, we conducted a laboratory experiment with human subjects to examine the potential
of introducing a proxy vote on behalf of future generations in order to increase the frequency with which
participants choose the sustainable alternative in the intergenerational sustainability dilemma game
(ISDG). We observed that under the traditional one-person-one-vote rule, the frequency of choosing thesustainable choice was extremely low and that the introduction of proxy votes increased this frequency
only slightly. This negative result is in contrast to the positive result reported in Hauser et al. [14].
We attribute this difference to differences in the basic structure of the games used in the two studies,suggesting that the ISDG in our study represents a more difficult situation for sustainability than the
IGG used in Hauser et al. [14]. In the ISDG, the majority of participants preferred the own-payoff
maximizing alternative, whereas a majority in the IGG preferred a sustainable choice.
In principle, voting is a means for collective decision-making that reflects the preference of the
majority. The key to sustainability issues from the perspective of majoritarianism is that, while amajority of a constituency that includes both the current generation and future generations may prefersustainable options even if they are costly to the current generation, a majority of the current generation
does not. Therefore, for sustainable options to be chosen in today’s society, it is necessary to either
somehow include future generations in the current decision-making process or change the preferencesof the majority of the current generation in a direction that is compatible with future generations.
The proxy vote examined in this paper was introduced as a way of including future generations in thevoting process. However, since it is ultimately members of the current generation who cast such proxyvotes, their preferences need to be compatible with future generations in order for the proxy voteapproach to succeed in selecting sustainable options. It has been thought that the introduction of proxyvotes would direct voters’ attention to the interests of future generations and result in the selectionof sustainable options. However, our experiment suggests that the provision of a proxy vote does
not have a sufficiently large effect on voter choices. As a future task, we need to develop a politicalinstitution that does not overly rely on, or rather brings out, the prosociality of the current generation
regarding future generations.
One of the changes that might activate such prosociality in the ISDG is to set voting more firmly
in the context of sustainability. In our experiment, we used terms such as “subsequent groups” rather
than “future generations.” However, if a proxy vote is introduced into an actual voting system, it
must be made clear that the proxy vote is for future generations rather than for “subsequent groups.”
Examining the effect of providing the context of sustainability and highlighting intergenerational issues
will be an important next step.
Author Contributions: Conceptualization, S.K. and Y.H.; methodology, S.K. and Y.H.; validation, S.K. and
Y.H.; investigation, S.K. and Y.H.; data curation, S.K.; resources, Y.H.; writing—original draft preparation, S.K.;
writing—review and editing, Y.H.; visualization, S.K. and Y.H.; supervision, Y.H.; project administration, S.K.;
funding acquisition, Y.H. All authors have read and agreed to the published version of the manuscript.
Funding: This research was funded by the Japan Society for the Promotion of Science (KAKENHI): Grant-in-Aid
for Scientific Research [C] 17K03769.
Acknowledgments: The authors are grateful to Toshiyuki Himichi, Yoshio Kamijo, Koji Kotani, Kengo Kurosaka,Nobuhiro Mifune, Yoshitaka Okano, Tatsuyoshi Saijo, Yuki Yanai, and two anonymous reviewers for theiruseful comments.

Acknowledgments: The authors are grateful to Toshiyuki Himichi, Yoshio Kamijo, Koji Kotani, Kengo
Kurosaka, Nobuhiro Mifune, Yoshitaka Okano, Tatsuyoshi Saijo, Yuki Yanai, and two anonymous reviewers fortheir useful comments.
Conflicts of Interest: The authors declare no conflict of interest. The funding source had no role in the design of
11 of 14the study, in the collection, analyses, or interpretation of data, in the writing of the manuscript, or in the decision
to publish the results.

Sustainability 2020, 12, 6311

Conflicts of Interest: The authors declare no conflict of interest. The funding source had no role in the design ofAppendixthestudy, inA
the collection, analyses, or interpretation of data, in the writing of the manuscript, or in the decision
to publish the results.

This appendix provides an English translation of the Japanese instructions used in our
experiment.
Appendix A The “attached table” in the instructions is Figure 1 of Kamijo et al. [9] with grid lines
added.
This appendix provides an English translation of the Japanese instructions used in our experiment.
InstructionsThe“attached table” in the instructions is Figure 1 of Kamijo et al. [9] with grid lines added.
Instructions(1) Outlineof the experiment(1) Outline of the experimentAs an
an honorarium
honorarium forAs
for participation
participation inin thisthis experiment,
experiment, 900
900 yenyen will
will bebe paid
paid toto eacheach participant.
participant.
We
will
pay
this
after
the
experimentis
over.
Additional
gratuities
willbedeterminedbythe choicechoiceWe will pay this after the experiment is over. Additional gratuities will be determined by the
explained below.
below.
explainedIn
this
In this experiment,
experiment, participants
participants inin thethe laboratorylaboratory will
will bebe randomly
randomly divided
divided into
into groups
groups ofof three.
three.
You
will
not
be
told
who
the
other
members
of
your
group
are.
You will not be told who the other members of your group are.
Each group
group chooses
chooses between
between alternatives
alternatives A
Depending onthat choice,choice, thethe gaingain will
will be
be
Each
A and
and B.
B. Dependingon thatdetermined.
Pleaseseetheattached
table.
The
numbers
in
this
table
are
in
hundreds.
For
example,27
determined. Please see the attached table. The numbers in this table are in hundreds. For example,
is 2700
yen.
If thefirst
groupchooses
2700 yen.
yen. EachEach27
is 2700
yen.
If thefirst
groupchoosesA,A,ititgains
gains3600
3600yen.
yen.IfIfititchooses
choosesB,
B, itit gains
gains 2700
group’s
choicewillbedecidedbyvoting.
The
additional
gratuityyoureceivewillbetheamountofgroup’s choice will be decided by voting. The additional gratuity you receive will be the amount of thethegainchosen
by
your
group
dividedequally
by
all
the
three
members.
gain chosen by your group divided equally by all the three members.
The figure
figure below
below shows
shows anan overview
overview ofof thethe experiment.
experiment. Your
group will
will bebe connectedconnected toto otherother
TheYour group
groupsthatareformedatothertimes.
For
example,suppose
that
your
group
is
the
third
group
groups that are formed at other times. For example, suppose that your group is the third groupinina
sequence of groups. Then, the gains from A and B for your group will change in response to thea sequence 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 yourchoices made at the previous times by the first and second groups of the sequence to which your group
group belongs. Note that for the first group there will be no effect from any previous groups because
belongs. Note that for the first group there will be no effect from any previous groups because it is theit is the first group in its sequence. Depending on the choice of your group, the gains from A and B
first group in its sequence. Depending on the choice of your group, the gains from A and B for thefor the subsequent groups of your sequence will change.
subsequent groups of your sequence will change.
Groups assembled at the same time in the laboratory will be given the same order in different
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 thesequences. Hence, the choices of other groups gathering in this laboratory now do not affect the choicechoice of your group. It is the choices of the previous groups in the same sequence that will influenceof your group. It is the choices of the previous groups in the same sequence that will influence your
your group’s choice. The choice of your group will also affect the choices of the subsequent groups
group’s choice. The choice of your group will also affect the choices of the subsequent groups in thein the same sequence.
same sequence.

(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 thefollowing table, the second group gains 2700 yen from A and 1800 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 other words, thesecond group gains 3600 yen from A and 2700 yen from B.

Sustainability 2020, 12, 6311

12 of 14

1st Group

2nd Group
A 2700 yen

A 3600 yen
B 1800 yen
A 3600 yen
B 2700 yen
B 2700 yen

Next, let us consider the third group. Now, suppose that the first group has chosen A. Then,the second group faces the choice in the shaded part of the table above. The table below shows thegains for the third group that follow the shaded part of the table above. Here, if the second groupchooses A, the gain from A for the third group decreases by 900 yen and becomes 1800 yen, and thegain from B also decreases by 900 yen and becomes 900 yen. On the other hand, if the second groupchooses B, the third group gains 2700 yen from A and 1800 yen from B.
2nd Group

3rd Group
A 1800 yen

A 2700 yen
B 900 yen
A 2700 yen
B 1800 yen
B 1800 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 thesame 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
the experimenters are strictly prohibited.
(3) Decision-making by each group
After the instructions, you will be given a sheet of paper on which the gains from A and B for yourgroup are written. These gains are determined by the choices of the previous groups, although thosefor the first group are known to be 3600 yen from A and 2700 yen from B. If the gain will be negative asa result of your group’s choice, you must pay it from your 900-yen honorarium for participation inthis experiment.
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 a majority of the 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, not 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 a majority of the 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 choicesby the groups who participated in this experiment before you. There are multiple possible combinations
for the choices of the previous groups. You will make voting decisions on all the cases that can arise.

Sustainability 2020, 12, 6311

13 of 14For 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,” “the firstgroup chose A and the second group chose B,” “the first group chose B and the second group 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 in 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 ExperimentX.
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 a majority of the votes will be the decision of your group. If a tie happens,a lottery 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 a majority of the votes will be the decision of your group. If a tie happens, a lottery will determine whichof the two 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 other words,
some participants make voting decisions in the order of “Experiment X → Experiment Y,” while theother 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 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][2]

Either Experiment X or Experiment Y is randomly selected.
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]
[2]
[3]
[4]

Out of the three members of your group, two members are assigned to Experiment X while one member isassigned to Experiment Y randomly.
The case that your group has faced is determined based on “the actual choices of the previous groups.”
The votes of all the group members in that case will be counted, and the choice of your groupis determined.
The resulting gain is divided into three equal parts, and each part is given to each of yourgroup members.

(5) Questionnaire
Once you have completed your voting decisions on all cases, you will receive a questionnairefrom an experimenter which you will be asked to complete.

Sustainability 2020, 12, 6311

14 of 14

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; pp. 253–260.
Van Parijs, P. The Disfranchisement of the Elderly, and Other Attempts to Secure Intergenerational Justice.
Philos. Public Aff. 1998, 27, 292–333. [CrossRef]
Aoki, R.; Vaithianathan, R. Sedaikan no Seiji Keizai: Senkyo ni kansuru Ankēto Chōsa kara (Intergenerational Political
Economy: From a Questionnaire Survey on Elections); Discussion Paper No. 540; Center for Intergenerational
Studies, Hitotsubashi University: Tokyo, Japan, 2009. (In Japanese)
Wolf, S.; Goldschmidt, N.; Petersen, T. Votes on Behalf of Children: A Legitimate Way of Giving Them a
Voice in Politics? Const. Political Econ. 2015, 26, 356–374. [CrossRef]
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. [CrossRef]
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: Kochi, Japan, 2015.
Miyake, K. Jikken kara Saguru Domein Tōhyō Hōshiki no Yūkōsei to sono Kadai (The Effectiveness andChallenges of the Demeny Voting System Explored Through an Experiment). Bachelor’s Thesis, Kochi
University of Technology, Kochi, Japan, 2015. (In Japanese).
Kamijo, Y.; Hizen, Y.; Saijo, T.; Tamura, T. Voting on Behalf of a Future Generation: A Laboratory Experiment.
Sustainability 2019, 11, 4271. [CrossRef]
Kamijo, Y.; Komiya, A.; Mifune, N.; Saijo, T. Negotiating with the Future: Incorporating Imaginary Future
Generations into Negotiations. Sustain. Sci. 2017, 12, 409–420. [CrossRef] [PubMed]
Nakagawa, Y.; Kotani, K.; Kamijo, Y.; Saijo, T. Solving Intergenerational Sustainability Dilemma through Imaginary
Future Generations: A Qualitative-Deliberative Approach; Discussion Paper SDES-2016-14; Kochi University ofTechnology: Kochi, Japan, 2016.
Shahrier, S.; Kotani, K.; Saijo, T. Intergenerational Sustainability Dilemma and the Degree of Capitalism inSocieties: A Field Experiment. Sustain. Sci. 2017, 12, 957–967. [CrossRef]
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: Kochi, Japan, 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 ofTechnology: Kochi, Japan, 2018.
Hauser, O.P.; Rand, D.G.; Peysakhovich, A.; Nowak, M.A. Cooperating with the Future. Nature 2014, 511,
220–223. [CrossRef] [PubMed]
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. J. Personal. Soc. Psychol. 1997, 73, 733–746.
[CrossRef]
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 of Technology: Kochi, Japan,
2020.
© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open accessarticle distributed under the terms and conditions of the Creative Commons Attribution(CC BY) license (http://creativecommons.org/licenses/by/4.0/).