>matU</code> . An
additional column <code>check_surv_gte_1</code> (produced with
<code>cdb_flag</code>) reports whether any <strong>single</strong> value
is greater than or equal to 1.</p>
</div>
<div class="section level3">
<h3 id="excessive-mortality">Excessive mortality<a class="anchor" aria-label="anchor" href="#excessive-mortality"></a>
</h3>
<p>At the opposite end of the survival spectrum, there may be some
matrices where some of the column sums of the <strong>U</strong> matrix
are zero, implying that