sydneyshares in commonwealth bank of australia fell early wednesday despite reporting an increase in margins as some analysts warned the growth may not be sustained the stock was down 30 at 10601 australian dollars us7470 it earlier hit a onemonth low of a10306 and is currently the fourthworst performer on the asx200 cba australias largest lender by market value on wednesday reported its net profit fell by 12 to a515 billion in the six months through december it raised its dividend by 20 to a210 a share which it attributed to continued balance sheet strength and its capital position the lender also said its net interest margin a measure of the difference between what a bank pays to get customer deposits and funds and what it charges to lend money was 18 basis points higher on year at 210 barrenjoey analysts jon mott and minh pham in an early take on the firsthalf result called out concerns around the monthly net interest margin with it peaking in october and falling after that the investment bank said this may lead to nim downgrades australian bank nims a key profitability indicator have significantly benefited amid sharply higher interest rates with the reserve bank of australia making nine consecutive interest rate increases but some analysts believe that intense competition on home loans and customer deposits may weigh on margins offsetting further rate hikes cba is up 33 so far this year