Make no mistake about it: Today marks one of the worst days of the year for the Dow Jones Industrial Average (^DJI 1.00%). Following a string of disappointing earnings releases among its component stocks, the blue-chip index is down more than 200 points, or 1.52%, as we approach the final hour of trading. The big question on investors' minds now is: How much lower could it go?

Why the Dow tanked today
The fact that American companies are reporting less-than-impressive third-quarter results should come as no surprise. At the beginning of September, analysts and commentators predicted the onset of an earnings recession. Not long afterward, a number of economic bellwethers publicly cut earnings forecasts for the remainder of the year. In the middle of September, for instance, both Intel (INTC 0.91%) and FedEx (FDX 3.77%) downgraded guidance, noting that the global economy is stalling and is bound to get worse.

The market's reaction to the earnings releases today nevertheless suggests that this was the first time traders had learned that worldwide demand is deteriorating. Early this morning, we heard from Dow heavyweights 3M (MMM 0.94%), United Technologies (RTX 1.42%), and DuPont (DD), all of which either disappointed analysts on the top or bottom line or decreased forward sales and/or profit guidance. DuPont, the hardest-hit of the three, said, "Weaker-than-expected demand in titanium dioxide and photovoltaic markets contributed to the decline from last year's record third-quarter earnings." Although most investors have no idea what those things are, suffice it to say that the overarching results shouldn't have come as a surprise to anyone.

To make matters worse, there's reason to believe that the market could continue its downward trajectory, as we're only approximately halfway through third-quarter earnings season. Up next among Dow companies are AT&T (T 0.27%) and Boeing (BA 5.93%), which report tomorrow, followed by Procter & Gamble (PG 0.78%) on Thursday and Merck (MRK 0.15%) on Friday. While the precise contours of their respective performances over the last three months are anybody's guess, given what we've seen so far, it's probably best to prepare for the worst.

The Foolish bottom line
All thing considered, it's been a tough earnings season thus far for stocks. It's for this reason that investors in companies like Intel and Boeing must stay up to date with the latest news regarding their companies. One way to do so economically is to download our in-depth reports on the companies -- Intel's is here, and Boeing's is here. As you'll see, these popular reports detail both the risks and benefits associated with owning shares in these industrial mavens.