Knowledge that Transforms

The current polarization of elites in the U.S., particularly in Congress, is frequently ascribed to the emergence of cohorts of ideologically extreme legislators replacing moderate ones. Politicians, however, do not operate as isolated agents, driven solely by their preferences. They act within organized parties, whose leaders exert control over the rank-and-file, directing support for and against policies. This paper shows that the omission of party discipline as a driver of political polarization is consequential for our understanding of this phenomenon. We present a multi-dimensional voting model and identification strategy designed to decouple the ideological preferences of lawmakers from the control exerted by their party leadership. Applying this structural framework to the U.S. Congress between 1927-2018, we find that the influence of leaders over their rank-and-file has been a growing driver of polarization in voting, particularly since the 1970s. In 2018, party discipline accounts for around 65% of the polarization in roll call voting. Our findings qualify the interpretation of -and in two important cases subvert -a number of empirical claims in the literature that measures polarization with models that lack a formal role for parties.

Changes in transport costs can affect mobility in ways that differ across the population, affecting the impacts of transport policies. We randomly assign large price reductions on Uber in Egypt over a 3-month period and collect comprehensive data on participant mobility using Google Timeline. A 50% price reduction quadruples Uber usage and induces a 42% increase in total travel. Effects and welfare gains are larger for women, who are less mobile at baseline and perceive public transit as unsafe. The price elasticity of private vehicle kilometers traveled (-1.28) implies that mobility and external costs increase substantially when ride-hailing prices fall.

Boys are less likely than girls to enter college, a gap that is often attributed to a lack of non-cognitive skills such as motivation and self-discipline.We study how being classified as gifted -determined by having an IQ score of 116 or higher -affects college entry rates of disadvantaged children in a large urban school district.For boys with IQ's around the cutoff, gifted identification raises the college entry rate by 25-30 percentage points -enough to catch up with girls in the same IQ range.In contrast, we find small effects for girls.Looking at course-taking and grade outcomes in middle and high school, we find large effects of gifted status for boys that close most of the gaps with girls, but no detectable effects on standardized tests scores of either gender.Overall, we interpret the evidence as demonstrating that gifted services raise the non-cognitive skills of boys conditional on their cognitive skills, leading to gains in educational attainment.