JP Morgan has downgraded Commonwealth Bank of Australia (ASX:CBA) to Underweight from Overweight - the broker notes that CBA has outperformed the bank index by 5% and rival bank Westpac (ASX:WBC) by 7% since the May bank updates. This suggests that a strong dividend is expected ahead of the CBA result, however, this has well been priced in by the market. As JP Morgan rates stocks relative to their sector, a downgrade to CBA has in turn been matched with an upgrade to Overweight for WBC. The CBA price target remains unchanged at $71.92 (current price $74.03). At the last closing share price CBA's estimated Price to Earnings Ratio is 16.20.