We examine friendships and study partnerships among university students over several years. At the aggregate level, connections increase over time, but homophily on gender and ethnicity is relatively constant across time, university residences, and different network layers. At the individual...

We examine how two highly successful new biotechnology firms (NBFs) source their most critical input -- scientific knowledge. We find that scientists at the two NBFs enter into large numbers of collaborative research efforts with scientists at other organizations, especially universities. Formal...

This paper uses the concept of the triad census first introduced by Holland and Leinhardt, and describes several distributions on directed graphs. Methods are presented for calculating the mean and the covariance matrix of the triad census for the uniform distribution that conditions on the...

We introduce the concept of a triad census of a digraph arid show how it can be used to enumerate various types of subgraph configurations. We give the basic probabilities needed for computing means and variances for a triad census under the U-MAN distribution for digraphs. These concepts are...

Entrepreneurs, particularly in the developing world, often hire from their networks: friends, family, and resulting referrals. Network hiring has two benefits, documented extensively in the empirical literature: entrepreneurs know more about the ability of their network (and indeed they are...

We use anonymized and aggregated data from Facebook to explore the spatial structure of social networks in the New York metro area. We highlight the importance of transportation infrastructure in shaping urban social networks by showingthat travel time and travel costs are substantially stronger...

In this paper, individuals are characterized by their identity -- an ideal code of conduct -- and by a level of tolerance for behaviors that differ from their own ideal. Individuals first choose their behavior, then form social networks. This paper studies the possibility of compromise, i.e....

Networking and the giving and receiving of advice outside of one's own firm are important features of entrepreneurship and innovation. We study how immigrants and natives utilize the potential networking opportunities provided by CIC, formerly known as the Cambridge Innovation Center. CIC is...

The nullification of slave wealth after the U.S. Civil War (1861-65) was one of the largest episodes of wealth compressions in history. We document that white Southern households holding more slave assets in 1860 lost substantially more wealth by 1870, relative to households that had been...

Social norms have the potential to alter the functioning of economic markets. We test whether norms shape the aggregate labor supply curve by leading decentralized individuals to maintain wage floors in their local labor markets. We partner with existing employers who create new jobs for workers...