Warehouse lines of credit extended by commercial banks to non-depository lenders fell a modest 11.8 percent in the fourth quarter on a sequential basis, but executives who work in the sector are reporting usage ratios as low as 20 percent. Based on exclusive survey figures compiled by Inside Mortgage Finance, warehouse providers had an estimated $30.0 billion in commitments at Dec. 31 compared to $34.0 billion at the end of the third quarter. But a commitment is...[Includes one data chart]