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.

Investors hadn't seen a month as bad as August was for the Dow Jones Industrials (DJINDICES:^DJI) in 15 months, with the Dow falling almost 4.5%. Even though the Dow remains up double-digit percentages for the year, the drop of 690 points has some investors wondering if the worst declines for the market are still in the future.

Several Dow components, however, posted much steeper losses. Let's look at the Dow's worst performers in August.

Hewlett-Packard (NYSE:HPQ) was by far the worst performer in the Dow in August, falling 13% for the month. The culprit was HP's earnings report, which scared shareholders and led to nearly all of the stock's loss in August. The company only managed to match earnings estimates and fell short with an 8% drop in revenue, but long-term investors should nevertheless take heart that HP remains disciplined in its turnaround strategy. Rather than using discounts to keep sales up, CEO Meg Whitman is focusing on keeping margins up and cutting costs -- strategies that should serve HP well in the long run.

JPMorgan Chase (NYSE:JPM) dropped 9.3% in August. Despite its best efforts to resolve outstanding disputes, JPMorgan continues to face new legal allegations. Early in the month, the bank said the Justice Department had targeted it in an investigation of its sales of mortgage-backed securities. Then mid-month, the SEC chimed in, investigating whether JPMorgan hired family members of government officials in China to get better treatment. Add to that an uncertain environment in the financial markets, and JPMorgan investors clearly want the bank to get itself under better control.

Cisco Systems (NASDAQ:CSCO) posted an 8.9% loss for the month, most of which resulted from its poor guidance in its quarterly report. Although the company beat expectations in the report, CEO John Chambers said sales growth at the networking giant will slow and that margins will probably remain flat. In addition, a dramatic set of layoffs that will reduce Cisco's workforce by 5% highlighted the need for the company to cut costs.

Finally, Johnson & Johnson (NYSE:JNJ) weighed on the Dow with a 6.9% drop. Once again, the company's Tylenol painkiller is in the news, as J&J is giving its bottles a new cap with warnings about the risks of taking too much of the over-the-counter drug. J&J faces dozens of lawsuits blaming Tylenol for injuries and deaths, while the FDA is considering new safety guidelines that could lead to less use of acetaminophen.

Fool contributor Dan Caplinger owns warrants on JPMorgan Chase. You can follow him on Twitter: @DanCaplinger. The Motley Fool recommends Cisco Systems and Johnson & Johnson and owns shares of Johnson & Johnson and JPMorgan Chase. Try any of our Foolish newsletter services free for 30 days. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.