Tobias J. Klein

The Effect of Private Health Insurance on Medical Care Utilization and Self-Assessed Health in Germany

In Germany, employees are generally obliged to participate in the public health insurance system, where coverage is universal, co-payments and deductibles are moderate, and premia are based on income. However, they may buy private insurance instead if their income exceeds the compulsory insurance threshold. Here, premia are based on age and health, individuals may choose to what extent they are covered, and deductibles and co-payments are common. In this paper, we estimate the effect of private insurance coverage on the number of doctor visits, the number of nights spent in a hospital and self-assessed health. Variation in income around the compulsory insurance threshold provides a natural experiment that we exploit to control for selection into private insurance. We document that income is measured with error and suggest an approach to take this into account. We find negative effects of private insurance coverage on the number of doctor visits, no effects on the number of nights spent in a hospital, and positive effects on health.

Upward Pricing Pressure in Two-Sided Markets

Pricing pressure indices have recently been proposed as alternative screening devices for horizontal mergers involving differentiated products. We extend the concept of Upward Pricing Pressure (UPP) proposed by Farrell and Shapiro (2010) to two-sided markets. Examples of such markets are the newspaper market, where the demand for advertising is related to the number of readers, and the market for online search, where advertising demand depends on the number of users. The formulas we derive are useful for screening mergers among two-sided platforms. Due to the two-sidedness they depend on four sets of diversion ratios that can either be estimated using market-level demand data or elicited in surveys. In an application, we evaluate a hypothetical merger in the Dutch daily newspaper market. Our results indicate that it is important to take the two-sidedness of the market into account when evaluating UPP.

The actual structure of eBay's feedback mechanism and early evidence on the effects of recent changes

eBay’s feedback mechanism is considered crucial to establishing and maintaining trust on the world’s largest trading platform. Yet, there is confusion among users about its exact institutional details, which changed substantially in May 2007. Most importantly, buyers now have the possibility to leave additional, anonymous ratings on sellers on four different criteria. We provide a thorough description of the institutional details of eBay’s feedback mechanism, including those changes. Then, we provide first descriptive evidence on the impact of those changes on rating behaviour.

Retirement and subjective well-being

We provide an explanation for the common finding that the effect of retirement on life satisfaction is negligible. For this we use subjective well-being measures for life and domains of life satisfaction that are available in the German Socio-Economic Panel (GSOEP) and show that the effect of voluntary retirement on satisfaction with current household income is negative, while the effect on satisfaction with leisure is positive. At the same time, the effect on health satisfaction is positive but small. Following the life domain approach we then argue that these effects offset each other for an average individual and that therefore the overall effect is negligible. Furthermore, we show that it is important to distinguish between voluntary and involuntary retirement. The effect of involuntary retirement is negative because the adverse effect on satisfaction with household income is bigger, the favorable effect on satisfaction with leisure is smaller, and the effect on satisfaction with health is not significantly different from zero. These results turn out to be robust to using different identification strategies such as fixed effects and first differences estimation, as well as instrumental variables estimation using eligibility ages and plant closures as instruments for voluntary and involuntary retirement.

Merger Simulation in a Two-Sided Market: The Case of the Dutch Daily Newspapers

We develop a structural econometric framework that allows us to simulate the effects of mergers among two-sided platforms selling differentiated products. We apply the proposed methodology to the Dutch newspaper industry. Our structural model encompasses demands for differentiated products on both sides of the market and profit maximization by competing oligopolistic publishers who choose subscription and advertising prices, while taking the interactions between the two-sides of the market into account. We measure the sign and size of the indirect network effects between the two sides of the market and simulate the effects of a hypothetical merger on prices and welfare.

Market Transparency, Adverse Selection, and Moral Hazard

We study how an improvement in market transparency affects seller exit and continuing sellers’ behavior in a market setting that involves informational asymmetries. The improvement was achieved by reducing strategic bias in buyer ratings. It led to a significant increase in buyer satisfaction with seller performance, but not to an increase in seller exit. When sellers had the choice between exiting—a reduction in adverse selection—and staying but improving behavior—a reduction in moral hazard—they preferred the latter. Increasing market transparency led to better market outcomes.

Price Competition in Two-Sided Markets with Heterogeneous Consumers and Network Effects

We model a two-sided market with heterogeneous customers and two heterogeneous network effects. In our model, customers on each market side care differently about both the number and the type of customers on the other side. Examples of two-sided markets are online platforms or daily newspapers. In the latter case, for instance, readership demand depends on the amount and the type of advertisements. Also, advertising demand depends on the number of readers and the distribution of readers across demographic groups. There are feedback loops because advertising demand depends on the numbers of readers, which again depends on the amount of advertising, and so on. Due to the difficulty in dealing with such feedback loops when publishers set prices on both sides of the market, most of the literature has avoided models with Bertrand competition on both sides or has resorted to simplifying assumptions such as linear demands or the presence of only one network effect. We address this issue by first presenting intuitive sufficient conditions for demand on each side to be unique given prices on both sides. We then derive sufficient conditions for the existence and uniqueness of an equilibrium in prices. For merger analysis, or any other policy simulation in the context of competition policy, it is important that equilibria exist and are unique. Otherwise, one cannot predict prices or welfare effects after a merger or a policy change. The conditions are related to the own- and cross-price effects, as well as the strength of the own and cross network effects. We show that most functional forms used in empirical work, such as logit type demand functions, tend to satisfy these conditions for realistic values of the respective parameters. Finally, using data on the Dutch daily newspaper industry, we estimate a flexible model of demand which satisfies the above conditions and evaluate the effects of a hypothetical merger and study the effects of a shrinking market for offline newspapers.

Ownership and control in a competitive industry

We study a differentiated product market in which an investor initially owns a controlling stake in one of two competing firms and may acquire a non-controlling or a controlling stake in a competitor, either directly using her own assets, or indirectly via the controlled firm. While industry profits are maximized within a symmetric two product monopoly, the investor attains this only in exceptional cases. Instead, she sometimes acquires a noncontrolling stake. Or she invests asymmetrically rather than pursuing a full takeover if she acquires a controlling one. Generally, she invests indirectly if she only wants to affect the product market outcome, and directly if acquiring shares is profitable per se.

Adverse Selection and Moral Hazard in Anonymous Markets

Abstract: We study the effects of improvements in eBay’s rating mechanism on seller exit and continuing sellers’ behavior. Following a large sample of sellers over time, we exploit the fact that the rating mechanism was changed to reduce strategic bias in buyer rating. That improvement did not lead to increased exit of poorly rated sellers. Yet, buyer valuation of the staying sellers—especially the poorly rated ones—improved significantly. By our preferred interpretation, the latter effect results from increased seller effort; also, when sellers have the choice between exiting (a reduction in adverse selection) and improved behavior (a reduction in moral hazard), then they prefer the latter because of lower cost.

Assessing Unilateral Merger Effects in the Dutch Daily Newspaper Market

The newspaper market is a typical example of a so-called two-sided market: publishers sell content to readers and advertising slots to advertisers, while taking into account that the demand for advertisements in a newspaper depends positively on its circulation and the demand of readers might be affected by the number (or concentration) of ads in the newspaper (Anderson and Gabszewicz, 2006). When it comes to assessing a proposed merger, competition authorities are, as a rule, required to establish whether a horizontal merger is likely to raise concerns with respect to unilateral or non-coordinated effects (that is, whether the merger might increase the market power of the merging firms) and with respect to coordinated or collusive effects (that is, whether the merger might make collusion more likely). With regard to the assessment of unilateral merger effects, competition authorities have devised different methods to address the issue. For instance, initial screening has traditionally been based on the analysis of the market shares of the merging parties and of (the changes in) the HerfindahlHirschman Index (HHI). Hence mergers among firms with market shares below a given threshold and mergers characterized by a post-merger HHI and a change in the HHI below certain thresholds have been almost automatically approved. For mergers judged to be worthy of further investigation, full merger simulations have only seldom been conducted. More often, preference has been given to a small but significant nontransitory increase in price (SSNIP)-type test, where it is asked whether the merging firms would find it profitable to raise prices post merger by a given threshold, usually 5 or 10 per cent, assuming rivals would not react.2