Even the company that runs the marketplace has to submit to the market's discipline. Motley Fool Rule Breakers pick NYSE Euronext (NYSE:NYX) came in $0.05 light on its second-quarter earnings per share compared to the consensus estimate of $0.78. As I write this, the shares are down 14%. That's the headline, but what should long-term shareholders and investors be looking at?

First, there are a lot of moving parts affecting earnings at NYSE Euronext because of acquisitions, dispositions, and cost reduction initiatives. Despite management's efforts to be transparent, these factors introduce volatility into the company's results that is hard to model. In that context, an earnings miss may reflect the fact that the business is in a transitional phase as much as it reflects disappointing performance.

Equities good, derivatives better
In absolute terms, the results look pretty decent with adjusted revenue and operating income increasing 12% and 10%, respectively, year over year. U.S. cash markets volume grew at 7%, less than half the growth in European cash market volume (17%). Buoyed by volatility in equity, credit, and commodity markets, volume growth at the firm's two derivatives arms, NYSE Arca (U.S) and Liffe (Europe), grew 38% and 22%, respectively.

Mind your share
One area of concern: NYSE's market share of matched transactions for NYSE-listed securities fell to less than half during the quarter, with Nasdaq capturing 22%. NYSE's loss in share is at least a five-year trend.

Shareholders or potential investors may want to track this number over the coming quarters. Continued declines in share raise questions about how defensible the franchise really is. (Full disclosure: I recommended Nasdaq Stock Market, now Nasdaq OMX (NASDAQ:NDAQ), in the May 2007 issue of Motley Fool Inside Value.)

Nasdaq OMX isn't the only wolf at the door. Witness the rise of nontraditional competitors such as Bats Trading and the multiplication of broker-dealer-led platforms here and in Europe. Lehman Brothers (NYSE:LEH), Goldman Sachs (NYSE:GS), Citigroup (NYSE:C), Merrill Lynch (NYSE:MER), and Morgan Stanley (NYSE:MS) are all participating in at least one project.

The exchanges look pretty darn cheap
Trading at 11.8 times estimated 2009 earnings prior to today's drop, NYSE Euronext looks pretty fetching right now. (At yesterday's close, Nasdaq's multiple was a nearly identical 11.7). Although I think there are lower-risk propositions in the market today, investors who missed the huge 2005-2006 run-up in NYSE Euronext shares have what looks like an acceptable entry point here.

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Alex Dumortier, CFA, has no beneficial interest in any of the companies mentioned in this article. Nasdaq OMX Group is a Motley Fool Inside Value pick. NYSE Euronext is a Motley Fool Rule Breakers recommendation. Try any of our Foolish newsletters today, free for 30 days, for some education, amusement, and enrichment during these choppy market times. We're all in it together, you know. The Fool has a disclosure policy.