Adjustable-rate mortgages dominated the Alt A collateral mix last year as borrowers continued to focus on affordability and low payments while seeking the flexibility of low and no-documentation options. A new Inside Alternative Mortgages snapshot of the Alt A market looked at the type of loans that were securitized by lenders last year. The data highlight a banner year for ARMs, which accounted for 70.9 percent of 2005’s total production – up from just… [One data table included]