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 continue to wait anxiously for news on whether the federal government will avoid default and reopen. The Dow Jones Industrials (DJINDICES:^DJI) have fluctuated wildly for weeks as conflicting reports about progress have come out, and today's swings between the unchanged level and an 85-point drop in the first 15 minutes of trading are the latest example of that volatility. As of 12:20 p.m. EDT, the Dow was down about 50 points.

This morning's earnings announcements might have played a role in keeping the Dow's downward movement from being more severe. Both Coca-Cola and Johnson & Johnson reported solid results, and both stocks were slightly higher at midday.

But tomorrow, IBM (NYSE:IBM) and American Express (NYSE:AXP) will add their names to the list of companies issuing their reports. Together, they'll add a new element to the Dow stocks we've already seen give their quarterly results.

IBM isn't likely to give investors much to worry about on the earnings front, as the tech giant continues to pull out all the stops to achieve its goal of $20 in annual earnings per share in 2015. Yet IBM has had trouble producing revenue growth, and analysts don't expect that to change this quarter, predicting flat sales. IBM's long-term strategic efforts have largely been successful, but now the company needs to use its cloud-computing potential to bolster its growth even in light of heightened competition. Otherwise, Big Blue could find itself falling behind the curve in the war among top tech companies.

Meanwhile, American Express aims to distinguish itself as a top card company despite facing much larger competitors in the card-network arena. AmEx still believes that combining merchant-network services and cardmember offerings under the same roof is the best path to profit, as it allows AmEx to reap the rewards of smart credit practices and also retain some transaction-based revenue that isn't subject to credit-quality cycles. Given improving credit conditions among its customers, AmEx hopes its expansion efforts will help it bring in more customers, and that could spell good news not just for AmEx but also for the health of the U.S. economy as a whole.

Fool contributor Dan Caplinger has no position in any stocks mentioned. You can follow him on Twitter @DanCaplinger. The Motley Fool recommends American Express, Coca-Cola, and Johnson & Johnson. The Motley Fool owns shares of IBM and Johnson & Johnson. Try any of our Foolish newsletter services free for 30 days. We Fools may not 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.