The increase of 4,172 inmates between December 31, 1990, and October 18, 1991, is an average increase of 435 a month. At this rate of increase, a new prison the size of Dartmoor would have to be opened every 6 weeks to provide space for additional prisoners. This year's steady increase in the prison population reverses the trend of the previous 2 years. The average prison population of England and Wales fell from a peak of 49,949 in 1988 to 48,610 in 1989 and 45,636 in 1990. There are normally seasonal fluctuations in the prison population in the course of each year. The number of inmates normally falls in December because of reduced activity by the courts over the Christmas period; it then rises between the beginning of the year and Easter, falls between Easter and the beginning of September, and then rises to a peak at the end of November, followed by the December fall. The rise in numbers between January and Easter could therefore be explained by seasonal factors; however, the post-Easter rise from 45,106 at the end of March 1991 to 46,310 at the end of August 1991 occurred at a time when the prison population usually falls. Seasonal trends suggest that the increase in numbers is likely to continue at least until the end of November. Week-by-week prison population figures are provided as well for the period from December 31, 1990, through October 18, 1991. 2 tables