reserving.TailBondy

The Bondy tail, as chainladder-python’s TailBondy.

Usage

reserving.TailBondy()

Each log factor from earliest_age on is taken as b times the one before it, b fitted by least squares. The fitted factors are f0 ** (b ** j) from the factor f0 at earliest_age, and those past the next one multiply to the last fitted factor raised to b / (1 - b). With the default earliest_age (the age of the last factor) b is 1/2 and the tail repeats the last factor.

Parameters

earliest_age: int

First age in months whose factor enters the fit (the last age at or before it, as chainladder-python reads it); the age of the last factor by default.

attachment_age: int

The factor from this age (the last age at or before it) to the next is kept and the fitted ones replace those after it; the age of the last factor by default. Not before earliest_age.

Examples

>>> from prospicio.reserving import ChainLadder, TailBondy, Triangle
>>> tri = Triangle.from_long(
...     [2020, 2020, 2020, 2021, 2021, 2022],
...     [12, 24, 36, 12, 24, 12],
...     [100.0, 150.0, 165.0, 110.0, 170.0, 120.0],
... )
>>> round(ChainLadder(tail=TailBondy()).fit(tri, "values").tail, 12)

1.1

Attributes

Name	Description
attachment_age	Age after which the fitted factors replace the estimated ones;
earliest_age	First age whose factor enters the fit; None is the age of the

---

attachment_age

Age after which the fitted factors replace the estimated ones;

attachment_age: int | None

None is the age of the last factor.

---

earliest_age

First age whose factor enters the fit; None is the age of the

earliest_age: int | None

last factor.