Person:

Gennaioli, N

We present a model of stereotypes in which a decision maker assessing a group recalls only that group’s most representative or distinctive types. Stereotypes highlight differences between groups, and are especially inaccurate (consisting of unlikely, extreme types) when groups are similar. Stereotypical thinking exhibits base rate neglect, but also confirmation bias: beliefs overreact to information that confirms the stereotype and ignore information that contradicts it. Stereotypes can change if new information changes the group’s most distinctive trait. Applied to gender stereotypes, the model provides a unified account of disparate evidence regarding the gender gap in education and in labor markets.

We investigate the evolution of common law under overruling, a system of precedent change in which appellate courts replace existing legal rules with new ones. We use a legal realist model, in which judges change the law to reflect their own preferences or attitudes, but changing the law is costly to them. The model's predictions are consistent with the empirical evidence on the overruling behavior of the U.S. Supreme Court and appellate courts. We find that overruling leads to unstable legal rules that rarely converge to efficiency. The selection of disputes for litigation does not change this conclusion. Our findings provide a rationale for the value of precedent, as well as for the general preference of appellate courts for distinguishing rather than overruling as a law-making strategy.

We present a model of market competition and product differentiation in which consumers' attention is drawn to the products' most salient attributes. Firms compete for consumer attention via their choices of quality and price. With salience, strategic positioning of each product affects how all other products are perceived. With this attention externality, depending on the cost of producing quality some markets exhibit "commoditized" price salient equilibria, while others exhibit "de-commoditized" quality salient equilibria. When the cost of producing quality changes, innovation can lead to a radical change in markets. In the context of financial innovation, the model generates the well documented phenomenon of "reaching for yield."

We use a newly assembled sample of 1,503 regions from 82 countries to compare the speed of per capita income convergence within and across countries. Regional growth is shaped by similar factors as national growth, such as geography and human capital. Regional convergence is about 2.5% per year, not more than 1% per year faster than convergence between countries. Regional convergence is faster in richer countries, and countries with better capital markets. A calibration of a neoclassical growth model suggests that significant barriers to factor mobility within countries are needed to account for the evidence.

We present a model of shadow banking in which banks originate and trade loans, assemble them into diversified portfolios, and finance these portfolios externally with riskless debt. In this model: outside investor wealth drives the demand for riskless debt and indirectly for securitization, bank assets and leverage move together, banks become interconnected through markets, and banks increase their exposure to systematic risk as they reduce idiosyncratic risk through diversification. The shadow banking system is stable and welfare improving under rational expectations, but vulnerable to crises and liquidity dry-ups when investors ignore tail risks.

Following legal realists, we model the causes and consequences of trial judges exercising discretion in finding facts in a trial. We identify two motivations for the exercise of such discretion: judicial policy preferences and judges’ aversion to reversal on appeal when the law is unsettled. In the latter case, judges exercising fact discretion find the facts that fit the settled precedents, even when they have no policy preferences. In a standard model of a tort, judicial fact discretion leads to setting of damages unpredictable from true facts of the case but predictable from knowledge of judicial preferences, distorts the number and severity of accidents, and generates welfare losses. It also encourages litigants to take extreme positions in court and raises the incidence of litigation relative to settlement, especially in new and complex disputes for which the law is unsettled.

We present a model of lawmaking by appellate courts in which judges influenced by policy preferences can distinguish precedents at some cost. We find a cost and a benefit of diversity of judicial views. Policy‐motivated judges distort the law away from efficiency, but diversity of judicial views also fosters legal evolution and increases the law’s precision. We call our central finding the Cardozo theorem: even when judges are motivated by personal agendas, legal evolution is, on average, beneficial because it washes out judicial biases and renders the law more precise. Our paper provides a theoretical foundation for the evolutionary adaptability of common law.