Pershing Square on MBIA and Ambac CDO losses

On January 30 Pershing Square released an open-source spreadsheet containing information on CDO guarantees written by MBIA and Ambac.

It's got 551 worksheets and occupies just under 128Mbytes. But it doesn't have to be so big. In 543 of those worksheets, there is space allocated to rows far beyond the last one with any data in it; and eight of the worksheets have many redundant columns to the right of the data too.

This fact can be found manually, on a given worksheet, by pressing CTRL-END, and seeing which rows and columns the cursor lands in. If it's far beyond the last occupied rows and columns, space is being wasted.

The same condition can be found automatically by any of several add-ins for Excel designed to aid development and testing of spreadsheets. They are rather necessary for a quantity of worksheets infeasibly large to explore by individually.

The space can be recovered by deleting the unnecessary rows and columns, saving the workbook, closing it and reloading it. Doing that to Pershing's spreadsheet reduces the size of the workbook to below 87Mbytes, which means that it contains 41Mbytes of fresh air.

That doesn't stop Pershing's work being an impressive piece of analysis.