HousingWire reports Citigroup decreased its troubled-mortgage portfolio by 45 percent over the first quarter a year ago, to $7.8 billion.  Of the $5.3 billion converted to modification loans, 75 percent were through the Home Affordable Modification Program (HAMP).  The redefault rate of the HAMP loans is 10 percent lower than of the other modified loans.  In addition, Citi sold $1.1 billion in delinquent mortgages during the first quarter, part of the $10 billion mortgages sold overall, $6 billion of which were delinquent.  Citi has cut its Holdings portfolio almost $500 billion since its peak of $827 billion five years ago, but it still recorded an earnings drop of 32 percent for the quarter.  It also recorded $151 million in buying back faulty mortgages, but that is a drop from the $235 million in the previous quarter.