The steady flow of small, frequent losses that gives a portfolio a stable, predictable average.
Attritional losses are the numerous, low-value claims whose regularity makes the law of large numbers work, as against the large one-off losses that carry away a whole year. Their presence is the condition of actuarial pricing, for it supplies an informative average and an estimable frequency. Some markets are deprived of them by construction, such as space insurance, where a portfolio of a few dozen objects each worth a year of premium knows only total loss, which makes it a gaming table rather than an insurance portfolio in the actuarial sense.
Unlike other markets, the space market has no attritional losses, it suffers large one-off claims capable of carrying away a carrier's whole year.
pertes attritionnelles, sinistres attritionnels