The pooling of logitudinal studies of aging.

This report describes the pooling of 5 longitudinal studies conducted during the last 20 years in West Germany. The pooling provides the following improvements: By increasing the number of participants the reliability and precision of the results are improved. The sample becomes representative of the whole area of the FRG. Both cohort and age comparisons are improved by extending their ranges. The time-of-testing range is increased from 5 to 17 years. Since the significance of this factor has been recognized often but since few empirical explorations have been made in the past, the extension of the time-of-testing range represents the most important contribution of the present work. The pooling of different studies is possible only if they share a common set of methods. This requirement is met under the present conditions. Moreover, each study adds unique methods to the pool, thus, supplementing the common explorations in a constructive manner.