A term used to describe the percentage of loans that do not close in a mortgage originator's pipeline. Mortgage originators adjust the fallout assumptions used in their hedge ratios as interest rates change relative to the loans they have in their pipelines. 

|||At the same time or shortly after a borrower locks in a mortgage rate with a mortgage lender, the lender typically lays off the risk that current interest rates might change relative to the interest rate given the borrower by putting on a hedge. The hedge is designed to last until the mortgage closes, at which point the mortgage can be sold into the secondary mortgage market and the hedge unwound. However, many loans that are locked in by borrowers do not end up closing. The percentage of loans that do not close after being locked is called fallout. Fallout assumptions are an important part of a mortgage lender's hedging efficiency.