Did the quarter-century anniversary of Black Monday, the Dow's worst single-day percentage decline, spook the market? I don't believe in superstition, but many investors do; I can't help but think this date was in the back of their minds as the Dow (DJINDICES:^DJI) registered a 1.52% decline -- its worst daily performance in four months. The S&P 500 (SNPINDEX:^GSPC) fared even worse, losing 1.66%.

The micro view: However, the market had more than just the specter of a crash to worry about. With a direct bearing on stock prices, disappointing earnings from three Dow bellwethers across different sectors of the economy must have weighed heavily on investor sentiment, as General Electric (NYSE:GE), Microsoft (NASDAQ:MSFT) and McDonad's (NYSE:MCD) all underperformed. Are GE and Microsoft shares a buy at current prices? Click here or here, respectively, to request the Motley Fool's premium reports on either stock, and you'll also receive a year's worth of updates.

The macro view: According to S&P Dow Jones Indices, more than a fifth (115) of the S&P 500 companies have now reported their results for the third quarter. On that basis, the estimate for third quarter earnings-per-share for the index came down slightly this week, from $25.02 to $24.82, as it did the previous week. However, estimates for the fourth quarter, and for 2014, remain (surprisingly) firm. The two sectors with the highest percentage of companies beating estimates so far are Consumer Staples and Financials. The former is consistent with a slowing economy, while the latter is more likely the product of sharply reduced guidance in the run-up to the earnings season.

Fool on and enjoy your weekend!

Alex Dumortier, CFA has no positions in the stocks mentioned above; you can follow him @longrunreturns. The Motley Fool owns shares of General Electric Company, McDonald's, and Microsoft. Motley Fool newsletter services recommend McDonald's and Microsoft. 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.