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Gain shifts in photomultipliers from count-rate changes can be minimized by using only five active stages, making up the gain with a low-noise preamplifier. Further reductions sometimes result from a dim light shining on the dynode structure. Reductions to less than 1 part in 600 were seen.

A revised notation is developed in which the accounting and model relationships that characterize multiregional population systems can be expressed. The variable K represents population as a stock, as a flow, and as an event count. People move from one state and location to another state and location over time. A special set of location—state labels for variable K describe the transitions possible. The hope is expressed that the notation will contribute to fruitful synthesis in the field of spatial demography.