ASTAM: Development and BF react differently to immature experience
Development methods extrapolate observed claims using a pattern. BF combines observed claims with expected unreported or unpaid claims. The reported fraction and expected ultimate assumption must refer to the same data basis.
Worked example or practice scenario
Expected ultimate claims are 1,000 and only 25% are expected reported. Actual reported claims are 300. Development ultimate is 300/.25=1,200; BF ultimate is 300+1,000×.75=1,050. These methods use current experience differently.
Try this next
Change reported claims to 200 and compare results. Then vary the expected ultimate assumption. A method comparison is not a vote: explain which data or assumption each method relies on and why one might be more stable at the selected maturity.
Reading sources
ActNet editorial guide · October 1, 2026 · Original illustrative examples.