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Steffen Ahrens

Overconfidence is one of the most important biases in financial decision making and commonly associated with excessive trading and asset price volatility. So far, most of the finance literature takes overconfidence as a given, “static” personality trait. Using a new experimental design, we show that trader overconfidence is endogenous and co-moves with asset prices; when asset prices go up, overconfidence rises, and when asset prices go down, overconfidence falls. Larger fluctuations in asset prices are met by larger changes in overconfidence. Hence, our results point towards a feedback loop in which overconfidence adds fuel to the flame of existing bubbles.

Josef Brüderl

A large interdisciplinary literature on the relationship between age and subjective well-being (happiness) has produced very mixed evidence. Virtually every conceivable age-happiness trajectory has been supported by empirical evidence and theoretical arguments. Sceptics may conclude that the social science of happiness can only produce arbitrary results. In this paper we argue that this conclusion is premature. Instead, the methodological toolbox that has been developed by the modern literature on causal inference gives scholars everything they need to arrive at valid conclusions: the causal inference toolbox only must be applied by happiness researchers. We identify four potential sources of bias that may distort the assessment of the age-happiness relationship. By causal reasoning we derive a model specification that avoids these biases. For an empirical illustration, we use the longest running panel study with information on happiness, the German Socio-Economic Panel (1984-2017; N persons=70,922; N person-years =565,703). With these data we demonstrate the relevance of the four biases and how combinations of different biases can reproduce almost any finding from the literature. Most biases tend to produce a spuriously U-shaped age trajectory, the most prominent finding from the literature. In contrast, with our specification we find a (nearly monotonic) declining age-happiness trajectory.

Jana Friedrichsen

Trust is thought to be an important driver of economic growth and other economic outcomes. Previous studies suggest that the decision to trust is driven by a combination of risk attitudes, distributional preferences, betrayal aversion, and beliefs about the probability of being reciprocated. We compare the results of a binary trust game to the results of a series of control treatments that remove the effect of one or more of these components of trust by design. This allows us to decompose variation in trust behavior into its underlying factors. Our results imply that beliefs are the main driver of trust, and that the additional components only play a role when beliefs about reciprocity are sufficiently optimistic. Our decomposition approach can be applied to other settings where multiple factors that are not independent amongst each other affect behavior. We analyze its advantages over the more traditional approach of including measures of relevant factors derived from separate tasks, in particular with respect to measurement error and omitted-variable bias.