Some aspects of the design and analysis of short panel data are considered. It is assumed that each individual may be at any instant in one of two states, for example employed and unemployed, and that individuals may switch from one to the other state. Alternative ways of observing individuals in discrete time are compared via the Fisher information matrix. The effect of the observational interval on the efficiency of the estimation is stressed and optimal time intervals for alternative sampling schemes are computed. A generalization to a model with covariates is outlined.