I haven’t watched Saturday Night Live for a long time, but I’ve been thinking about a classic line from the show’s Weekend Update sketch. Back in 1988, during the Winter Olympics, Dennis Miller opened his sportscast like this: “In Calgary tonight, Katarina Witt won the gold medal in figure skating, prompting Yankees owner George Steinbrenner to fire manager Billy Martin.”

If you’re not a baseball fan, the joke needs an explanation. Billy Martin was the manager of the New York Yankees during five separate stints beginning in 1975. The mercurial Steinbrenner fired Martin in 1978, rehired him in 1979, fired him again after 95 games, then hired and fired him three more times in 1983, 1985 and 1988. No one knows exactly what reasons Steinbrenner used to justify all those firings, but Katarina Witt’s gold medal performance in Calgary seems as good as any.

I remembered the joke this morning when I read the Financial Post’s daily market commentary: “The S&P 500 added more than 2% in the two previous sessions as immediate concerns over rising yields in Spain and Italy ebbed and on bets the Chinese GDP data would surprise on the upside.”

This commentary can sound so knowledgeable and wise. But to suggest that daily market movements can be explained in such simple cause-and-effect terms is laughable. If you want proof, all you need to do is read the commentary every day. You’ll just as often see statements like this: “The S&P 500 shed more than 2% in the two previous sessions despite immediate concerns over…”

It can’t work both ways: either these events affect daily stock prices, or they don’t. Once you accept this, you realize that commentary linking the S&P 500 to surprising Chinese GDP data sounds a lot like the joke about Katarina Witt and Billy Martin.

Here’s my own version of the daily market report: “The S&P 500 added more than 2% during the last two sessions because of an incredibly complex and largely random combination of factors that cannot possibly be distilled into one sentence. Analysts expect gains to continue during the second quarter, but since this is already priced into the markets, no one should give a fiddler’s fart what they think. Meanwhile, money managers have released their forecasts for the year, which will be widely read and acted upon, despite the fact that their previous forecasts were dead wrong. Tune in tomorrow for more of the same. In the meantime, stick to your long-term plan.”