In the transition from an industrial society to a service society, particularly changes on the labour market are likely to occur. A number of authors assert that these changes will result in an increasing external-numerical flexibility, which is assumed to affect labour market processes in terms of generally higher labour market mobility and decreasing employment stabil-ity (Speeding-up-Thesis). The consequence of this process is said to be a levelling out of employment opportunities and risks; uncertainties that in industrial societies were unevenly distributed along clearly defined socio-economic demarcation lines are said to be becoming increasingly generalised. The old division between core and peripheral workforces is said to be dissolving into general employment instability (De-Structuring-Thesis). Therefore, the dissertation investigates into the individual and firm specific determinants of job stability and how these determinants maybe have changed over time by estimating transition rate models to test both hypotheses. For this reason the event history data of the IAB Employment Subsample (IABS) is used. The results are very different from those one would expect from the de-stabilisation hypothesis and the de-structuring hypothesis. There is no evidence for socio-economic de-structuring, but rather for a socio-economic re-structuring process. This restructuring process has simultaneously led to an increasing polarisation and to an increasing levelling out of employment chances and risks.