Stocks ended a lackluster week on a down note as unimpressive earnings kept investors wary and news about the US economy left them uninspired. Trading was light, and earnings season was nearly over. Those still at work remarked on the difference that just a week made — the S&P 500 and the Dow Jones industrial average both hit their highest closing levels exactly one week before. Looking ahead, the Commerce Department reports on July retail sales Tuesday and on housing starts on Friday. Companies releasing earnings this week include Cisco and Walmart — both closely watched for clues about where the broader economy is headed.