UBS AG Total Exposure to Credit Risk

While checking out EDGAR, I finally found the UBS Annual Report of 2007. They are holding a total credit Risk of 1.5 Trillion according to International Financial Reporting Standards (IFRS). See this chart. For an overview of the latest issued stock Options, see this and this. What I find interesting is that the amount of stock Options issued between 2005 and 2007 is massive in comparison to the other years. To me it resembles something of a Checkout. Also note that UBS started a share buyback program in 2006 and 2007 witch obviously is not good for the company (according to Warren Buffett) and just drives up the Stock price artificially and makes the option value higher. I can hardly imagine that this was a coincidence. Compare  this to Citigroups exposure.