Over the past four years, the number of insurance companies joining Federal Home Loan Banks has grown by an average of about 10 percent as several insurance groups have substantially increased their borrowing capacity within the FHLBank system, and there is more where that came from, according to a report by Fitch Ratings. Among the 17 top insurance company FHLBank borrowers at year-end 2012, Fitch noted that only one was not a life insurance company. "Life insurance companies dominate insurance company FHLB advance usage, mostly due to the presence of housing-related assets in their investment portfolios,” said Fitch. “Life insurers are usually more likely than other insurers to invest in this sector due to their need for long-duration investment assets to match against the long-duration and cash flow characteristics of their insurance liabilities.”