the <strong>U</strong> matrix)
from a particular stage cannot exceed 1. However, in some cases, errors
in the original matrices (including data entry and rounding errors)
cause this situation to occur and may persist in the data set. We can
check for this error using column sums of the <strong>U</strong> matrix,
and may wish to exclude matrices with any column sum greater than
1.<br>
This issue is examined using the column <code>SurvivalIssue</code> which
gives the maximum value of the column sums for <code