I couldn't find a stat on the total amount in guarranteed mutual fund investments/seg funds, but I did find some stats for the seg fund industry in Canada in 2006/2007 alone:

Total net sales for the entire industry reached $2.8 billion at June 30, 2007, handily surpassing the $2.1 billion in net sales generated in the same period last year. According to the most recent Investor Economics data available at press time, the staggering growth of 33.3% corresponds to one of the largest increases in net sales seen since the early 1990s. http://www.insurance-journal.ca/arch...

Apparently seg funds do exist in the U.S. too, but I'm not sure how popular they are.