Are the self-employed really jacks-of-all-trades? Testing the assumptions and implications of Lazear's theory of entrepreneurship with German data

Using a large representative German data set and various concepts of self-employment, this paper tests the 'jack-of-all-trades' view of entrepreneurship by Lazear (AER 2004). Consistent with its theoretical assumptions we find that self-employed individuals perform more tasks and that their work requires more skills than that of paid employees. In contrast to Lazear's assumptions, however, self-employed individuals do not just need more basic but also more expert skills than employees. Our results also provide only very limited support for the idea that human capital investment patterns differ between those who become self-employed and those ending up in paid employment. -- Unter Verwendung eines großen, repräsentativen Datensatzes für Deutschland und verschiedener Abgrenzungen der Selbständigkeit überprüft diese Arbeit die 'jack-of-all-trades'-Sicht des Unternehmertums von Lazear (AER 2004). In Übereinstimmung mit ihren theoretischen Annahmen finden wir, dass Selbständige mehr verschiedene Tätigkeiten ausüben und Kenntnisse aus mehr verschiedenen Gebieten benötigen als nicht-selbständige Arbeitnehmer. Im Gegensatz zu Lazear's Annahmen benötigen Selbständige allerdings nicht nur mehr Grundkenntnisse sondern auch mehr Fachkenntnisse als Nicht-Selbständige. Unsere Ergebnisse liefern zudem nur wenig Unterstützung für die Behauptung, dass sich die Muster der Humankapitalaneignung zwischen Selbstständigen und abhängig beschäftigten Arbeitnehmern sichtbar unterscheiden.entrepreneurship,self-employed,Germany

Establishment Exits in Germany: The Role of Size and Age

Using comprehensive data for West Germany, this paper investigates the determinants of establishment exit. We find that between 1975 and 2006 the average exit rate has risen considerably. In order to test various "liabilities" of establishment survival identified in the literature, we analyze the impact of establishment size and put a special focus on differences between young and mature establishments. Our empirical analysis shows that the mortality risk falls with establishment size, which confirms the liability of smallness. The probability of exit is substantially higher for young establishments which are not more than five years old, thus confirming the liability of newness. There also exists a liability of aging since exit rates first decline over time, reaching a minimum at ages 15 to 18, and then rise again somewhat. The determinants of exit differ substantially between young and mature establishments, suggesting that young establishments are more vulnerable in a number of ways.firm exits, Germany

Are the self-employed really jacks-of-all-trades? Testing the assumptions and implications of Lazear's theory of entrepreneurship with German data

Using a large representative German data set and various concepts of self-employment, this paper tests the jack-of-all-trades view of entrepreneurship by Lazear (AER 2004). Consistent with its theoretical assumptions we find that self-employed individuals perform more tasks and that their work requires more skills than that of paid employees. In contrast to Lazear's assumptions, however, self-employed individuals do not just need more basic but also more expert skills than employees. Our results also provide only very limited support for the idea that human capital investment patterns differ between those who become self-employed and those ending up in paid employment. -- Unter Verwendung eines großen, repräsentativen Datensatzes für Deutschland und verschiedener Abgrenzungen der Selbständigkeit überprüft diese Arbeit die jack-of-all-trades-Sicht des Unternehmertums von Lazear (AER 2004). In Übereinstimmung mit ihren theoretischen Annahmen finden wir, dass Selbständige mehr verschiedene Tätigkeiten ausüben und Kenntnisse aus mehr verschiedenen Gebieten benötigen als nicht-selbständige Arbeitnehmer. Im Gegensatz zu Lazear's Annahmen benötigen Selbständige allerdings nicht nur mehr Grundkenntnisse sondern auch mehr Fachkenntnisse als Nicht-Selbständige. Unsere Ergebnisse liefern zudem nur wenig Unterstützung für die Behauptung, dass sich die Muster der Humankapitalaneignung zwischen Selbstständigen und abhängig beschäftigten Arbeitnehmern sichtbar unterscheiden.entrepreneurship,self-employed,Germany

Invariance of waveguide grating mirrors to lateral displacement phase shifts

We present a method to analyse the coupling of lateral displacements in nanoscale structures, in particular waveguide grating mirrors (WGM), into the phase of a reflected Gaussian beam using a finite-difference time-domain simulation. Such phase noise is of interest for using WGMs in high-precision interferometry. We show that WGMs do not couple lateral displacements into the phase of a reflected beam to a precision of 10^{-7} rad and that WGMs are therefore not subject to the same stringent alignment requirements as previously proposed layouts using diffraction gratings.Comment: 3 Pages, 4 figure

Birefringence Measurements on Crystalline Silicon

Crystalline silicon has been proposed as a new test mass material in third generation gravitational wave detectors such as the Einstein Telescope (ET). Birefringence can reduce the interferometric contrast and can produce dynamical disturbances in interferometers. In this work we use the method of polarisation-dependent resonance frequency analysis of Fabry-Perot-cavities containing silicon as a birefringent medium. Our measurements show a birefringence of silicon along the (111) axis of the order of $\Delta\, n \approx 10^{-7}$ at a laser wavelength of 1550nm and room temperature. A model is presented that explains the results of different settings of our measurements as a superposition of elastic strains caused by external stresses in the sample and plastic strains possibly generated during the production process. An application of our theory on the proposed ET test mass geometry suggests no critical effect on birefringence due to elastic strains.Comment: 19 pages, 6 figures, 2 table

Tomographic readout of an opto-mechanical interferometer

The quantum state of light changes its nature when being reflected off a mechanical oscillator due to the latter's susceptibility to radiation pressure. As a result, a coherent state can transform into a squeezed state and can get entangled with the motion of the oscillator. The complete tomographic reconstruction of the state of light requires the ability to readout arbitrary quadratures. Here we demonstrate such a readout by applying a balanced homodyne detector to an interferometric position measurement of a thermally excited high-Q silicon nitride membrane in a Michelson-Sagnac interferometer. A readout noise of \unit{1.9 \cdot 10^{-16}}{\metre/\sqrt{\hertz}} around the membrane's fundamental oscillation mode at \unit{133}{\kilo\hertz} has been achieved, going below the peak value of the standard quantum limit by a factor of 8.2 (9 dB). The readout noise was entirely dominated by shot noise in a rather broad frequency range around the mechanical resonance.Comment: 7 pages, 5 figure