A version of the "stability of punishment" hypothesis is used to illustrate the concept of cointegration and its relationship to error correction models. This theory suggests that imprisonment rates rise and fall according to exogenic factors such as prison capacity, in order to keep prison populations at a stable level. Thus, the threshold of punishable behavior is adjusted, officially or unofficially. There was no empirical evidence to support this theory. A dynamic time-series model is developed and tested, which relates imprisonment to convictions, crime, and unemployment. This model attributes imprisonment rate changes not to workload, but to judicial attitudes and ideological positions. It cites deteriorating economic conditions, the volume of recorded crime, and its amplification by mass media as reasons for more frequent use of severe sanctions. 4 tables, 50 references. (Author abstract modified)