Although we don't believe in timing the market or panicking over daily movements, we do like to keep an eye on market changes -- just in case they're material to our investing thesis.

The Dow Jones Industrial Average (DJINDICES:^DJI) plummeted today, falling 225 points, or 1.5%, as investors worried that consumers were cutting back on their spending after disappointing reports by Wal-Mart (NYSE:WMT) and other retailers.

Reporting earnings this morning, Wal-Mart said it missed on both top and bottom lines, and lowered its full-year outlook. The world's largest retailer earned $1.24 per share, missing estimates by a $0.01, while revenue increased 2.4%, to $116.2 billion, below expectations of $118.1 billion. Same-store sales also fell at Wal-Mart's U.S. stores for the second quarter in a row, declining by 0.3%. That figure is closely watched because nearly 10% of non-automotive consumer spending in the U.S. takes place at Wal-Mart, and economists see it as a bellwether for the economy as a whole. The company blamed the slowdown on the payroll tax increase and higher gas prices, and it now expects a full-year sales increase of just 2%-3%, instead of the previously forecasted 5%-6%. It also cut its EPS forecast to $5.10-$5.30, from $5.20-$5.40, and shares finished down 2.6%.

Despite the sell-off, there was some good news today. Initial unemployment claims fell to a new six-year low, down to 320,000, better than estimates of 339,000. That also brought the four-week moving average to a near six-year low at 332,000, a sign that the labor market is steadily improving, which should help consumer spending. Elsewhere, the Empire State manufacturing report beat estimates, but the Philadelphia Fed's manufacturing index missed, though it still showed strong growth. Finally, the consumer price index edged 0.2% in July, matching projections, and homebuilder confidence jumped.

Wal-Mart wasn't the only Dow stock to slide today. Hewlett-Packard (NYSE:HPQ) shares finished down 4.5% as rival Lenovo, which recently replaced HP as the world's top PC seller, said it sold more smartphones and tablets than PCs in its recent quarter. Lenovo also saw just a 1.4% decline in computer shipments, compared to an 11% overall decline in the market, indicating that HP may have seen a steeper drop than expected. After hours, Dell, the No. 3 PC maker, reported that profits dropped 72%, and PC revenue fell 5%, as it faces many of the same challenges as HP. Hewlett-Packard will report earnings next Wednesday; analysts are expecting a per-share profit of $0.87.

Finally, Cisco Systems (NASDAQ:CSCO) shares ended down 7.2% after the networking leader said that it would lay off 4,000 employees. The news was surprising as it came on an otherwise solid earnings report, but CEO John Chambers said his company was still facing headwinds from the recovering economy.