pergeneration

Pergeneration is a compound term used in technical writing to describe a metric, rate, or quantity measured per generation. While not a formal unit in most standards, it appears in fields such as genetics, demography, epidemiology, and linguistics to facilitate comparisons across generations and to align analyses with generational timescales.

In genetics, the phrase is often used in the context of per-generation mutation rates. The human per-generation mutation rate is commonly cited as roughly 60–100 de novo mutations per genome per generation, corresponding to an approximate per-base rate on the order of 1×10^-8. This framing helps researchers compare mutational load across species or populations, or to study the effects of parental age and other factors on the mutation burden passed to offspring.

In demography, pergeneration measurements relate to fertility, reproduction, and population growth structured around generation length. Generation time varies by population but is frequently estimated in the mid-twenties to early thirties for modeling purposes. Pergeneration rates can be used to translate annual demographic rates into generational terms, aiding policy analysis and historical comparison.

In epidemiology, pergeneration concepts appear in discussions of the spread of infectious diseases, where R0 or generation-based reproduction numbers describe how many secondary cases arise per generation of transmission. In linguistics and cultural evolution, pergeneration rates may describe language change or cultural transmission across generations.

Limitations include the lack of a universally fixed generation length, which makes pergeneration metrics sensitive to the chosen generation interval and context. Nevertheless, the term serves as a useful heuristic for cross-generational analysis when clearly defined.