as January goes ...

There's this saying among investors: "As January goes, so goes the year"

Meaning: If January is a good (or bad) month, then the whole year will be good (or bad).

>Is it true?
How would I know? I can only look at a particular market over a particular time period and generate some numbers, like so:

Note that we're looking at the returns for the month of January (from Open to Close) and those for the entire year.

>Seems like a good bet, eh?
You bet, I'll observe.

>But what about next year?
Wait'll I check.

There's a spreadsheet, but you'll need 60 year's worth of monthly data from Yahoo:   Click!

Then you might check out: Sell in May then Go Away  

Some interpret "As January goes, so goes the year" to mean "As January goes, so goes the rest of the year".
I interpret it to mean "... so goes the year".