tail_extrapolation
Fit exponential or inverse-power tail models to late development factors and extrapolate to estimate the tail factor for chain-ladder reserving.
Instructions
Fit parametric tail models to the late development factors and extrapolate forward. Pro tier.
Fits two candidate models — exponential decay
(ln(f_j - 1) = a + b·j) and inverse-power
(ln(f_j - 1) = a + b·ln(j+1)) — picks the better R², and
returns the implied tail factor for plugging back into
compute_chain_ladder(tail=…).
Use this when the triangle obviously hasn't reached ultimate by the last observed development period — i.e., the last selected factor is still meaningfully above 1.
Args: selected_factors: The factor set you want to extrapolate from. n_extra: How many extra development periods to project. Default 6 (covers most P&C lines).
Returns either:
- On success: {fits[], recommended, summary} — each fits
entry has model, parameters, r_squared,
extrapolated[], tail_factor.
- On license failure: {error, status}.
Input Schema
| Name | Required | Description | Default |
|---|---|---|---|
| selected_factors | Yes | ||
| n_extra | No |
Output Schema
| Name | Required | Description | Default |
|---|---|---|---|
No arguments | |||