Inertia is the weight given to existing
non-fasttrack case reserve, when calculating next case reserve. Inertia monthly
values are applied under "Type" object.
The formula to implement inertia is:
Reserve(t) = Inertia(t--1) * Reserve(t-1)+
(1-Inertia(t-1)) * (Indicated Reserve(t)),
Indicated Reserve(t) is the indicated value gpt after applying the reserve
adequacy multiplier and Reserve(t-1) is the prior period reserve after
applying this inertia formula.