PhD graduates are twice as likely to be placed at a university if their PhD advisor has a co-author there. The importance of the collaboration network for placement has doubled between 1990 and 2014. Network hires are positively selected on observables, but we find no evidence for revelation of private information about graduates.

We study a reform that eased cross-border commuting from France to the high-wage Swiss labour market. Using a difference-in-differences strategy comparing the French border region with the unaffected French inland, we find that wages increase among mid- and low-skill workers employed in the French border region. Employment in the French border region does not decline overall and increases particularly for low-skill workers. Both local labour supply and demand adjust substantially. Labour supply increases through the local population and the labour force participation rate. Firms increase sales and productivity more than wages, implying that the labour share did not rise. The results thus show that if labour supply is elastic enough, the local labour market can expand and absorb additional competition for workers.

We show that differential IT investment across cities has been a key driver of job and wage polarization since the 1990s. Using a novel data set, we establish two stylized facts: IT investment is highest in firms in large and expensive cities, and the decline in routine cognitive occupations is most prevalent in large and expensive cities. To explain these facts, we propose a model mechanism where the substitution of routine workers by IT leads to higher IT adoption in large cities due to a higher cost of living and higher wages. We estimate the spatial equilibrium model to trace out the effects of IT on the labor market between 1990 and 2015. The decline in IT prices alone accounts for about 30 percent of the stronger displacement of routine cognitive jobs in expensive locations.

Labor market dynamism, measured by flows of workers between employers, declined substantially in the US and employment polarized into low and high-skill jobs. This paper shows the two trends are linked. I provide a framework to study employment and worker flows in presence of two-sided heterogeneity. Within an estimated version of the framework I find that routine-biased technological change accounts for about one-third of the decline in job-to-job mobility for workers without a college degree, while the remaining decline in mobility is mainly driven by a decline in the dispersion of match-specific productivity and its innovation rate.

Large cities are more productive and generate more output per person. Using data from the UK on energy demand and waste generation, we show that they are also more energy-efficient.