New issuance of prime non-agency MBS remained at historically high levels during the first quarter of 2006, thanks to a healthy supply of nontraditional mortgage loans, according to a new ranking and analysis based on the Inside Mortgage Finance MBS Database. A total of $142.93 billion of so-called private-label MBS were issued during the first three months of 2006, a 15.6 percent increase over the same period last year. Quarterly volume burst past the $100… [Two data tables included]