 there is no survival from that particular stage.
This may be a perfectly valid parameterisation for a particular
year/place but is biologically unreasonable in the longer term and users
may wish to exclude problematic matrices from their analysis. This issue
is indicated by the column <code>check_zero_U_colsum</code>.</p>
</div>
<div class="section level3">
<h3 id="irreducibility-and-ergodicity">Irreducibility and ergodicity<a class="anchor" aria-label="anchor" href="#irreducibility-and-ergodicity"></a>
</