Subprime lenders grew their businesses at a fevered clip last year, posting record volume at a time when overall mortgage originations took a plunge, a new Inside B&C Lending analysis and ranking reveals. On a yearly basis, subprime originations grew by an estimated 59.6 percent, to $529.90 billion, in 2004. Somewhat surprisingly, $277.9 billion of that volume came in the second half of the year. After dipping by 8.8 percent between the second and…