1. RISE and FALL of COOPERATION Jun Kobayashi (Seikei U) Yuhsuke Koyama (Tokyo I of Tech) Hideki Fujiyama (Dokkyo U) Hirokuni Oura (Teikyo U) August 15, 2005 ASA, Philadelphia

2. OVERVIEW  Mutual Effects of Group Cooperation Rate & Group Size? (traditional)  Social Dilemma Experiment w/ Intergroup Mobility (Not traditional)

3. 3  Olson... Size↑→Cooperation↓  Free-rider Problem, Social Dilemma  Counter Effect?  Modern Societies… Exit Option  Moving, Job change, Divorce  Effect of Group Cooperation Rate on Group Size??? QUESTION

4. ON the RUN (Erhart + Keser)  Experiment, Intergroup Mobility  9 players in 3 group, 10 Sessions  Cooperators RUN AWAY  Cycle: Size↑→Cooperation↓→ S↓→C↑  Various Conditions???

5. Introduction Data Result

6. 6  2003/4, 4 universities in Japan  10 Sessions, 170 Students  ¥ 1289.0 ($11), 90 minutes  Computer-based, Group data  “LOW” “MIDDLE” “HIGH” Mobility  17 in 4 Groups, Anonymous  10 Rounds, 9 Exit chances EXPERIMENT

7. 7

8. 8 ROUND (10 times) A B C D Exit Chance Free-rider Problem

9. 9  Resource ¥ 20  PROVIDE or NOT  Pooled Resources...  DOUBLED...3/more-player groups  x 1.5... 2-player Groups  SAME... 1-player Groups  EQUALLY Distributed in Group 1. FREE-RIDER PROBLEM

10. 10  Provide = 40m/4 = 10m (Providers)  Not = 40(m-1)/4 + 20 = 10m + 10 Not Provide Not x 2 = EXAMPLE (4 Players)

11. 11  LOW Mobility... ¥ 50 to Exit  MIDDLE Mobility... ¥ 20  HIGH Mobility... ¥ 0 2. EXIT CHANCE

12. A 33.33 B 25.00 C 27.50 D 25.00 A 33.33 B 25.00 C 27.50 D 25.00 A 3 B4 C8 D 2 Groups’ Average Payoffs Last Stage Groups’ Average Payoffs in This Round Groups’ Size Group C Round 2 Stage 2 Your Decisions and Payoffs in This Round StageYour DecisionYour Payoff 1NOT35.00 2PROVIDE 5.00 Your Total: 125 yens ( 20 yens subtracted for Moving) Group C's Members: You (ID 6) and Other 7 What do you do next stage? PROVIDE 20 yens NOT

13. Provided 20 yens: 3 persons Not: 4 persons Your Decision: Provide Your Payoff: 17.14 yens

14. A 30.00 3 B 33.33 4 C 25.00 8 D 27.50 2 Groups’ Average Payoffs and Size last Round ROUND END Groups’ Average Payoffs GroupStage 12345 A 33.33 20.00 15.55 24.76 35.00 B 25.00 35.00 19.10 35.00 C 27.50 22.00 27.50 20.00 D 25.00 35.00 25.00 18.88 Your payoff Last Round: 112 yens in Group C Which Group in Next Round? Move with 50 yens Group A B C D

15. HYPOTHESES  H1. Size↑→Cooperation↓  H2. Cooperation↓→ Size↓  H3. Mobility↑→Cycle Accelerated Size Cooperation Rate H1 H2 H1 H2

16. REGRESSION ANALYSES  Unit… Group (N=360)  H1. Size↑ Cooperation↓ Round Number, Previous Cooperation  H2. Previous Coop.↓ Size↓ Round Number, Previous Size

17. Introduction Data Result

18. 18 DESCRIPTIVE STAT.

19. H1. SIZE on COOPERATION

20. y = COOPERATION RATE ＊ p<.05, ＊＊.01, ＊＊＊.001 Mobility Cost ¥ 50 ¥ 20 ¥0¥0 ROUND.00 SIZE-.04***-.05***-.03* Previous COOP..47***.11-.04 R2R2.32.16.11

21. H2. COOPERATION on SIZE Size Previous Cooperation Rate

22. y = SIZE ＊ p<.05, ＊＊.01, ＊＊＊.001 Mobility Cost ¥ 50 ¥ 20 ¥0¥0 ROUND.00-.01.07 Previous COOP. 2.12***3.11***4.83*** Previous Size.83***.65***.36** R2R2.60.37.27

23. H3. MOBILITY on CYCLE

24.  Interaction Effects… Not Significant

25. EXAMPLES of CYCLE (LOW) Group A B C D

26. MIDDLE MOBILITY

27. HIGH MOBILITY

28. 28  Large Groups DECREASE Cooperation, then SHRINK  Then INCREASE Cooperation, then EXPAND  MOBILITY ACCELERATES Cycle SUMMARY