The Dynamics of Seller Reputation: Theory and Evidence from eBay

We propose a basic theoretical model of eBay's reputation mechanism, derive a series of implications and empirically test their validity. Our theoretical model features both adverse selection and moral hazard. We show that when a seller receives a negative rating for the first time his reputation decreases and so does his effort level. This implies a decline in sales and price; and an increase in the rate of arrival of subsequent negative feedback. Our model also suggests that sellers with worse records are more likely to exit (and possibly re-enter under a new identity), whereas better sellers have more to gain from buying a reputation' by building up a record of favorable feedback through purchases rather than sales. Our empirical evidence, based on a panel data set of seller feedback histories and cross-sectional data on transaction prices collected from eBay is broadly consistent with all of these predictions. An important conclusion of our results is that eBay's reputation system gives way to strategic responses from both buyers and sellers.

Spin-offs: theory and evidence from the early U.S. automobile industry

We develop "passive learning" model of firm entry by spin-off : firm employees leave their employer and create a new firm when (a) they learn they are good entrepreneurs (type I spin-offs) or (b) they learn their employer's prospects are bad (type II spin-offs). Our theory predicts a high correlation between spin-offs and parent exit, especially when the parent is a low-productivity firm. This correlation may correspond to two types of causality: spin-off causes firm exit (type I spin-offs) and firm exit causes spin-offs (type II spin-offs). We test and confirm this and other model predictions on a unique data set of the U.S. automobile industry. Finally, we discuss policy implications regarding "covenant not to compete" laws. ; Also issued as a Payments System Research Working Paper

Dynamic Price Competition with Network Effects

I consider a dynamic model of competition between two proprietary networks. Consumers die and are replaced with a constant hazard rate. Firms compete for new consumers to join their network by offering network entry prices (which may be below cost). New consumers have a privately known preference for each network. Upon joining a network, in each period consumers enjoy a benefit which is increasing in network size during that period. Firms receive revenues from new consumers as well as from consumers already belonging to their network. Using a combination of analytical and numerical methods, I discuss various properties of the equilibrium. I show that very small or very large networks tend to price higher than networks of intermediate size. I also show that, around symmetric states, the gap between the large and the small network tends to widen (increasing dominance) whereas the opposite is true (reversion to the mean) around very asymmetric states

We're Number 1: Price Wars for Market Share Leadership

I examine the dynamics of oligopolies when fi rms derive subjective value from being the market leader. In equilibrium, prices alternate in tandem between high levels and occasional price wars, which take place when market shares are similar and market leadership is at stake. The stationary distribution of market shares is typically multimodal, that is, much of the time there is a stable market leader. Even though shareholders do not value market leadership per se, a corporate culture that values market leadership may increase shareholder value. From a competition policy point of view, the paper implies that price regime change dynamics and parallel pricing are consistent with competitive behavior -- in fact, hyper-competitive behavior