External population supplied by belt removal ($n_{\mathrm{out}}=T{n}_b/t_y$)

A population supplied at differential number rate $n_b(D)/t_y(D)$ and surviving externally for a size-independent time $T$ has $n_{\mathrm{out}}(D)=T{n}_b(D)/t_y(D)$. Its differential number slope changes by the negative of the removal-time exponent, unless the belt is already removal-dominated, in which case it reflects the fragment injection spectrum.