Das Ziel dieser Thesis ist es, Angebots- und Nachfragefaktoren in Deutschland seit der Wiedervereinigung zu analysieren. Drei verschiedene Arbeitsmarktmodelle dienen dazu: Ein Wettbewerbsmodell (Marshall (1920)), ein rigides Arbeitsmarktmodell (Pigou (1933)) und ein Matchingmodell (Pissarides (2000)). Unterschiedliche Hypothesen über den Zusammenhang von mehreren Arbeitsmarktindikatoren werden theoretisch hergeleitet und empirisch evaluiert. Diese Arbeit adressiert drei Forschungsfragen: Welcher Art ist das große Beschäftigungswachstum in Deutschland nach 2005? Waren Angebots- oder Nachfragefaktoren wichtiger für die Lohnspreizung nach 2003? Welche der zwei Hypothesen ist plausibel? a) Ein negativer Schock auf die Lohnstarrheit wegen sinkender Gewerkschaftsmacht und/oder beschäftigungsbewussten Lohnabschlüssen oder b) ein positiver Arbeitsangebotsschock aufgrund von Arbeitsmarktreformen. Die Antworten auf die drei Fragen sind: Das Beschäftigungswachstum seit 2005 vollzog sich primär über eine Ausweitung der Erwerbstätigen durch mehr Teilzeitarbeit. Die Lohnspreizung auch für Teilzeitbeschäftigte, welche mit einem eigens erstellten synthetischen Datensatz untersucht wird, begann 2003 und endete 2011. Die Kovariation des deutschen Arbeitsmarkts in dieser Zeit, also negative Korrelationen von Löhnen mit Beschäftigungs- bzw. Partizipationsmaßen, passen am besten zu einem Wettbewerbsmodell mit dominanten positiven Arbeitsangebotsschocks. Interpretation ist, dass diese positiven Angebotsschocks durch die Arbeitsmarktreformen induziert wurden. / The goal of this thesis is to analyze labor demand and labor supply factors in Germany since reunification. It is based on three different labor market frameworks: a competitive labor market model (Marshall (1920)), a rigid labor market model (Pigou (1933)), and a search-and-matching model (Pissarides (2000)). Differing hypothesis about the co-variation of labor market indicators are derived theoretically, and are evaluated empirically. Three research questions are addressed in this thesis: What is the nature of the large expansion of employment in Germany after 2005? Were supply or demand factors more important for the increase in employment and wage dispersion after 2003? Which of the two competing hypotheses is more plausible? a) A negative shock to wage rigidity due to declining union power and/or more employment-conscious wage bargaining, or b) a positive labor supply shock due to changes in labor market policies. The main findings corresponding to the three stated research questions are: The expansion of employment in Germany since 2005 has primarily been at the extensive margin due to the increase of part-time employment. The Dispersion of hourly wages, which is expanded in a synthetic panel to include part-time employment, began in 2003 and ended in 2011. The labor market outcomes in Germany in this period, namely the negative correlation of wages with employment and participation, correspond most closely to the competitive labor market model with dominant supply shocks. These positive labor supply shocks are interpreted to be induced by major labor market reforms.

My research seeks to understand the behaviour of workers and firms and how their decisions affect labour market outcomes. My PhD dissertation consists of three separate Chapters that use detailed historical, census and administrative data to gain insights into the mechanisms at play when incentives for production and location decisions change. Chapter 1 asks whether financial incentives can induce inventors to innovate more. I exploit a large reduction in the patent fee in the United Kingdom in 1884 to distinguish between its effect on increased efforts to invent, and a decrease in patent quality due to a lower quality threshold. For this analysis I create a detailed new dataset of 54,000 British inventors with renewal information for each patent. In the longer run high-quality patenting increases by over 100 percent, and the share of new patents due to greater effort accounts for three quarters of the pre-reform share of high-quality patents. To test for the presence of credit constraints I generate two wealth proxies from inventor names and addresses, and find a larger innovation response for inventors with lower wealth. These results indicate efficiency gains from decreasing the cost of inventing and in addition, from relaxing credit constraints. In Chapter 2 we assess the effects of changes in ethnic neighbourhood composition in England and Wales. A change in social housing allocations in the 1990s serves as instrument for changes in the local ethnic composition. For the analysis we create a dataset of highly disaggregated census geographies for 1991-2011. The results imply that an exogenous increase in social housing minority share by 10 percentage points raises the minority share in private housing by 1.2 percentage points initially. This sorting effect is larger for privately rented than for privately owned housing. We further show that an increase in the minority share leads to higher local population growth and a small decrease in house prices in the longer run. Chapter 3 proposes a new approach for analysing responses to comprehensive labour market reforms. Using detailed micro data we evaluate the German Hartz reforms that aimed at reducing unemployment. The timing of the reforms affects the model parameters, which are estimated using matched data on 430,000 workers in 340,000 firms. Contrary to previous findings, our analysis shows that the reforms marginally reduced unemployment at the cost of a pronounced decline in wages. Low-skilled workers suffered the largest wage losses. Furthermore, we decompose the contribution of each reform wave on employment and wages, and document a structural shift in the factors that govern overall wage dispersion.