JPMorgan on Friday reported a 23 percent decrease in profits for the last three months of 2011 as a result of big losses in its investment-banking and trading divisions. JPMorgan, the nation’s largest bank by assets, said it earned $3.7 billion, down from $4.8 billion in the same period in the previous year—a decrease of 23 percent. Net income from the bank dropped 52 percent to $726 million, which includes a $567 million drop that occurred from a debit-valuation adjustment. JPMorgan claimed that without those adjustments, there would be $1.1 billion earnings in its banking division. Net income from the bank dropped 40 percent to $302 million in the fourth quarter. JPMorgan CEO Jamie Dimon said in a statement that the bank is seeing signs of improvement in loan demand and credit quality.