Expected generation size in a Galton-Watson process (source code)

= Expected generation size in a Galton-Watson process
{title2=$\mathbb E[Z_n]=m^n$}

If a <Galton-Watson process> starts from one individual and has offspring mean $m$, conditioning on generation $n$ gives $\mathbb E[Z_{n+1}\mid Z_n]=mZ_n$. Induction therefore gives $\mathbb E[Z_n]=m^n$.