We investigate regional differences in the effect of new business formation on employment growth in West Germany. We find an inverse Ushaped relationship between the level of start-up activity and employment change. The main variables that shape the employment effects of new businesses in a region are population density, the share of medium-skilled workers, the amount of innovation activities as measured by the proportion of research and development (R&D) employees, and an entrepreneurial character of the regional technological regime. In contrast, a high share of small-business employment has a negative influence on the employment effect of start-ups. Other indicators for education, innovation activity, and labor productivity do not prove to be statistically significant.1 Aims and scope 1 Recent empirical research strongly indicates that the effect of new business formation on economic development is of a long-term nature.2 It is found that start-up rates may have a statistically significant impact on growth for a period of up to 10 years (for an overview, see Fritsch 2008). Over this time span, the effect of start-ups on growth shows considerable variation that is in most cases (countries or regions) characterized by a wave-like pattern (see Sect. 2 for details). This wave-like pattern reveals that new businesses have a positive impact on economic development in the first 1 or 2 years after formation, but that the effect then declines and, in many cases, becomes negative. In many regions, the effect becomes positive again after about 5 years, and then A. Schroeter e-mail: alexandra.schroeter@uni-jena.de 1 We are indebted to Oliver Falck (CES-ifo, Munich), Stephan Heblich (MPI, Jena), Antonio Garcia-Tabuenca (University of Alcala, Madrid), and two anonymous referees for their helpful comments on an earlier version of this manuscript. Oliver Falck also provided very valuable advice on econometric issues.

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a b s t r a c tAr + and He + ions were implanted into Ge samples with (1 0 0), (11 0), (111) and (11 2) orientations at 15 K with fluences ranging from 1 Â10 11 to 1 Â10 14 cm À 2 for the Ar + ions and fluences ranging from 1 Â10 12 to 6 Â 10 15 cm À 2 for the He + ions. The Rutherford backscattering (RBS) technique in the channelling orientation was used to study the damage built-up in situ. Implantation and RBS measurements were performed without changing the target temperature. The samples were mounted on a four axis goniometer cooled by a close cycle He cryostat. The implantations were performed with the surface being tilt 71 off the ion beam direction to prevent channelling effects. After each 300 keV Ar + and 40 keV He + implantation, RBS analysis was performed with 1.4 MeV He + ions.For both the implantation ions, there is about no difference between the values found for the damage efficiency per ion for the four different orientations. This together with the high value (around 5 times higher than that found in Si), gives rise to the assumption of amorphous pocket formation per incident ion, i.e. direct impact amorphization, already at low implantation fluences. At higher fluences, when collision cascades overlap, there is a growth of the already amorphized regions.

Ar+ ions were implanted into Ge samples with (100), (110), (111) and (112) orientations at 15 K with fluences ranging from 1 × 1011 to 1 × 1014 cm−2. The Rutherford backscattering (RBS) technique in the channelling orientation was used to study the damage build‐up in situ. Implantation and RBS measurements were performed without changing the target temperature. The samples were mounted on a four axis goniometer cooled by a close cycle He cryostat. The implantations were performed with the surface being tilted 7° off the ion beam direction to prevent channelling effects. After each 300 keV Ar+ implantation, RBS analysis performed with 1.4 MeV He+ ions. The damage efficiency per ion was found to be Pa =4.5 × 10−14 cm−2. There is no significant difference in the values found for the four different orientations. This, together with the high value (5 times higher than that found in Si), gives rise to the assumption of amorphous pocket formation per incident ion, i.e. direct impact amorphisation, already at low implantation fluences. At higher fluences, when collision cascades overlap, there is a growth of the already amorphised regions. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)