generationsintervall

Generationsintervall, or generation interval, is a concept used in demography, population genetics, and epidemiology to denote the characteristic time between the birth of an individual and the birth of its offspring. It can be viewed as the average age of parents at the birth of their children and, in population genetics, as the average time between successive generations in a reproductive population. The interval depends on the species’ reproductive schedule and survivorship patterns.

In demography, generation interval T is often defined as the average age of mothers at childbirth and can be estimated from age-specific survivorship l_x and maternity m_x with T = sum(x * l_x * m_x) / sum(l_x * m_x). In a stable population, T is related to the net reproductive rate R0 and the intrinsic growth rate r by T ≈ ln(R0)/r. In epidemiology, the term generation interval describes the time between successive infections in a transmission chain and is influenced by biology, behavior, and contact patterns.

Generation interval determines how fast a population or a pathogen can change generation by generation. Shorter intervals yield more generations per year, which can accelerate evolutionary responses and affect projections of population size or disease spread. Typical values vary widely: for humans the interval is often around 25–30 years, while for many infectious diseases it can be days to weeks, depending on the pathogen and transmission dynamics.