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.

Last week the Dow Jones Industrial Average (DJINDICES:^DJI) trended upward as optimism flooded the markets regarding a potential deal to raise the federal debt ceiling. Talks on Capitol Hill stalled over the weekend and the markets took an early dip into negative territory this morning. The Dow has rebounded and is trading 0.4% higher as of 2:45 p.m. EDT. Investors hoping for a deal to be made before we get ridiculously close to Thursday's default deadline are likely to be disappointed. As politicians continue to work out a deal regarding the debt ceiling, and as earnings season kicks into full gear, expect some volatility in the market going forward. With that in mind, here are some of today's biggest movers and shakers.

Boeing (NYSE:BA) is one of the Dow's biggest winners today, trading up nearly a full percentage point. This comes even though Boeing may have to furlough workers in its defense, space and security unit if the government's partial shutdown continues, according to Bloomberg. That's an additional blow to Boeing's defense business following the already planned $1 trillion in government defense spending cuts over the next nine years.

Boeing bears continually remark that its defense business could drag the company down over the short and medium terms. It's a valid point, to be sure. In 2010, defense, space and security represented 50% of the company's revenue, but that shrank to 38% as of last quarter. Morningstar analysts expect the segment to shrink further, representing an estimated 32% of Boeing's revenue in 2015 -- a rough decline in just five years.

Fortunately for Boeing investors, the company predicts that its commercial aviation business is set to surge as emerging markets grow their airline fleets and mature markets replace existing fleets. Boeing anticipates the world's commercial aircraft fleet to double over the next 20 years, worth an estimated $4.8 trillion. Investors seem to be buying into the estimates as Boeing's stock price is currently flirting with 52-week highs.

Pharmaceutical giant Pfizer (NYSE:PFE) is the biggest winner on the Dow this afternoon, trading 1.29% higher. This comes after last week's announcement of mixed results on Pfizer's tofacitinib drug. The drug was proven as effective as the blockbuster Enbrel at high doses, but less effective at lower doses. Analysts predict the mixed results will limit the demand for tofacitinib as a psoriasis medication.

"As a result, there is a risk that only the 5 milligram dose is approved in psoriasis and dermatologists will view (tofacitinib) to be inferior to Enbrel and other biologics with a similar and less robust pool of long-term safety data," ISI Group analyst Mark Schoenebaum said, according to Reuters.

Investors have so far shrugged off the news, and rightfully so. Pfizer has gained a vast competitive advantage with its massive financial resources in an industry where it takes many attempts to hit a blockbuster drug. Furthermore, Pfizer's pipeline of potential drugs -- which includes potential blockbuster drugs Xeljanz and Eliquis for rheumatoid arthritis and atrial fibrillation -- is quickly developing into one of the best in the industry.

Fool contributor Daniel Miller has no position in any stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. 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.