Retrospective Adjustment
To correct for retrospective bias in estimated initial abundance, AGEPRO applies multiplicative bias-correction coefficients. Let \(\underline{C}\) denote the vector of age-specific correction factors applied to \(\underline{N}(1)\). The bias-corrected initial population vector \(\underline{N^C}(1)\) is calculated from the element-wise product of \(\underline{N}(1)\) and \(\underline{C}\) as
\[ \underline{N^C}(1) = {\bigl( C_1N_1(1), \ \dots,\ C_aN_a(1),\ \dots,\ C_AN_A(1) \bigr)} \tag{12}\label{eq:12} \]
The bias-correction coefficients are applied to each initial population vector.
If bias is constant across ages, the vector simplifies to
\[ \underline{N}^*(1) =\ C \cdot\underline{N}(1) \tag{13}\label{eq:13} \]
Bias correction is applied only in the first projection year to account for systematic estimation bias in the starting population. Further discussion of retrospective adjustment is provided by (Mohn 1999).