The Dow Jones Industrials (DJINDICES:^DJI) continued to fall at midday Tuesday, building on losses from yesterday and dropping back down below the 17,000 mark. Even as investors continue to watch economic data for signs of the strength of U.S. economic expansion, the official beginning of earnings season comes this afternoon when Alcoa (NYSE:AA) reports its quarterly results. Even though Alcoa is no longer a member of the Dow Jones Industrials, the aluminum company still provides key insight into the health of the materials sector, and that in turn could give insight on a wide variety of blue-chip stocks. In particular, Boeing (NYSE:BA) investors will want to watch closely to see what Alcoa's results say about the market for basic materials and the potential for price hikes for the aluminum components the aerospace company needs for its aircraft.

Source: Alcoa.

Alcoa will report after the market closes, with its earnings release typically coming just a few minutes after 4 p.m. EDT. The former Dow component will follow up its release with a conference call scheduled to begin at 5 p.m. EDT.

Investors have high hopes for Alcoa earnings, with most expecting a solid boost in earnings from year-ago levels despite slightly weaker revenue. That's part and parcel of Alcoa's broader strategy, in which the aluminum producer has emphasized the higher-margin value-added side of its business, with customized products for the heavy-trucking, automotive, and aerospace industries taking the lead over the more commoditized area of making basic aluminum materials. By doing so, Alcoa expects to tap into the strong demand in those industries, with Boeing in particular representing a multitrillion-dollar opportunity in the commercial aircraft market. Aluminum has long played an important role in aerospace, but automakers are looking more seriously at the lightweight metal as well, with the need to boost fuel efficiency outweighing the higher cost compared to heavier metals such as steel. Alcoa has answered with strategic moves to emphasize its presence in those key industries.

Source: Alcoa.

Many investors also believe that Alcoa will start to see better pricing in the broader aluminum market, which could help bolster its overall results. One key problem for Alcoa has been that Chinese manufacturers have boosted supply even at rock-bottom prices, contributing to a global glut that has coincided with a slower pace of economic growth around the world. Yet as Alcoa takes advantage of cost-cutting measures of its own, the company is learning to adapt even to the tough price environment.

More broadly, Alcoa's results will give investors in the Dow Jones Industrials a useful look at the general level of economic activity over the past quarter. With many worried about the plunge in U.S. gross domestic product in the first quarter, Alcoa's results could give blue-chip investors their first concrete evidence about the second quarter; if the expected rebound does materialize, it could help send the entire Dow higher as investors would equate Alcoa strength with improving conditions throughout the economy.

Even though it's no longer in the Dow, Alcoa will nevertheless move the Dow tomorrow. With so many market participants looking at the aluminum giant as a bellwether for the stock market as a whole, Alcoa still wields a lot of influence as the first-mover of earnings season.

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