This paper considers a dynamic model of the evolution of open source software projects, focusing on the evolution of quality, contributing programmers, and users who contribute customer support to other users. Programmers who have used open source software are motivated by reciprocal altruism to...

A large literature following Hirsch (2005) has proposed citation-based indexes that could be used to rank academics. This paper examines how well several such indexes match labor market outcomes using data on the citation records of young tenured economists at 25 U.S. departments. Variants of...

This paper provides a critical review of models of the spread of the coronavirus (SARS-CoV-2) that have been influential in recent policy discussions. It notes potentially important features of the real- world environment that the standard models do not incorporate and discusses reasons why...

This paper explores differences in the frequency with which students from different schools reach high levels of math achievement. Data from the American Mathematics Competitions is used to produce counts of high-scoring students from more than two thousand public, coeducational, non-magnet,...

This paper provides a critical review of models of the spread of the coronavirus (SARS-CoV-2) that have been influential in recent policy discussions. It notes potentially important features of the real- world environment that the standard models do not incorporate and discusses reasons why...

Technological progress builds upon itself, with the expansion of invention in one domain propelling future work in linked fields. Our analysis uses 1.8 million U.S. patents and their citation properties to map the innovation network and its strength. Past innovation network structures are...

We study the prevalence and traits of global collaborative patents for U.S. public companies, where the inventor team is located both within and outside of the United States. Collaborative patents are frequently observed when a corporation is entering into a new foreign region for innovative...

We examine immigrant entrepreneurship and the survival and growth of immigrant-founded businesses over time relative to native-founded companies. Our work quantifies immigrant contributions to new firm creation in a wide variety of fields and using multiple definitions. While significant...

The global distribution of talent is highly skewed and the resources available to countries to develop and utilize their best and brightest vary substantially. The migration of skilled workers across countries tilts the deck even further. Using newly available data, we first review the landscape...

We study the relationship between ethnicity, occupational choice, and entrepreneurship. Immigrant groups in the United States cluster in specific business sectors. For example, the concentration of Korean self-employment in dry cleaners is 34 times greater than other immigrant groups, and...