Class:  The first figure below shows  the results of our Public vs. Private investing.  Below is the frequency of choices for investment in the public good, Investment B.  As you can see, Nash equilibrium, that is G=0, is the most frequent choice.  But there are also significant numbers who invest all 10 in the public good, an extreme act of generosity, and a good number who are split and put 5 in each.  This indicates a diversity of preferences for sharing.  The results below are fairly typical. 

You might ask, what happens with replication?  More experience tends to push choices toward G=0, but not all the way.  This is shown in the second figure below.  The "subj= " tells you how many players are in each group, and "MR= " tells you how much the public good paid relative to the private good.  Our example in class had an MR=1/2, since the public good (Investment B) paid half as much as the private good (Investment A), and had subj=5.