The reason for the spread of the losses across the world was the high degree of securitization of the U.S. mortgages. The process of home ownership in the U.S. involves a loan originator, using money from an original lender for the mortgage. The original lender rarely holds the loan, instead bundling mortgages into a Mortgage Backed Security (MBS).This practice enables the loan originator to continue lending, thereby increasing the availability of mortgage funds. The loan originator charges a fee, but does not end up with the risk of the loan not being repaid.The fact that the loan originator did not end up holding the mortgage resulted in less careful screening of individuals applying for home loans.