The added bounce the private-label MBS market received from a handful of portfolio restructuring deals in 2000 helped give the sector a strong ARM flavor and pulled some business away from private conduits. Adjustable-rate mortgages accounted for 23 percent of the private-label MBSs issued last year, according to a new analysis by Inside MBS & ABS. That was up from just 10 percent in 1999, with most of the ARM MBS production for the year