LoanPerformance, a company whose extensive loan database tracks 80 percent of the non-agency MBS market, this week officially joined the race to develop a prepayment score that it hopes will become an industry standard much in the way Fair Isaac has done with its popular FICO credit score. The San Francisco-based LoanPerformance appears to have a leg up on competitors in that it hosts the largest mortgage database in the country – nearly 50 million