Altruism with Social Roots: An Emerging Literature
Pablo Branas-Garza y Maria Paz Espinosa
from reciprocity and from the friendship effect. This is interesting in
the sense that in a setting where there is no room for strategic behavior,
at least in the short term, individuals with high social integration find
it in their interest to be generous18.
II. Puzzles
The above literature reports some alternative sources of social giving:
whereas GMMTY, MRQ and BDE support the friendship effect (so-
cial proximity), which explains why individuals always help those
subjects linked to them, BCEJP focus on social integration regardless
of social proximity.
To shed some light on this question, we use previous experimental
data (BDE) but control for social integration and other variables re-
garding the matching mechanism. In the BDE design, after the net-
work elicitation stage individuals play a dictator game either with a
randomly chosen friend or with a stranger. The subjects know whether
pi( f ) = 1 or pi( f ) = 0; however, they do not have information about
the recipient’s identity, 0 < pi( j) ≤ 1.
We use the following explanatory variables:
• Social Proximity: pi( f ) is a dummy variable which takes the value
1 if the subject faces a friend for sure or 0 whenever he/she faces
a stranger.
• Social Integration: fi or degree - out is the number of friends that
the individual has in the network, i.e. the number of links arising
from the subject, |Fi|.
• Reciprocity: pi( j) is the probability of being matched to a specific
friend; this variable takes the following values.
for pi(f) = 0 → pi( j) = 0
for pi( f ) = 1 → pi( j) = 1/fi
18 It is worth noting that an alternative measure of social integration, degree-out, turns out
not to be statistically significant in explaining giving. In this respect see also the discussion
at the end (Section III).
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