> This report must keep a running total of data by column.

To get a running total, you either need to calculate each total by summing
all the previous entries (which involves n*n/2 operations), or you need
recursion, passing the current total as a parameter at each recursive step.

Interestingly, running totals are one of the few examples I found where
linear head-tail recursion (recursive processing of a sequence) is still
needed in XSLT 2.0.

Michael Kay