Credit Suisse is using cheesecake to determine sales at Nordstrom

When Nordstrom stopped reporting monthly same-store sales, a very important number for investors, an alternative had to be found.

The answer was cheesecake, or The Cheesecake Factory to be exact.

The Cheesecake Factory still reports monthly same-store sales in its quarterly report, often a few weeks ahead of Nordstrom.

"As we have generally considered Nordstrom's customer to be similar to The Cheesecake Factory's (CAKE) customer, we took a deeper look at just how profound the overlap actually is," Michael Exstein, a Credit Suisse analyst, said in a note to clients.

"We found from our analysis that the historical [comparable same-store] sales are in fact very closely correlated, as the companies' store locations are for the most part in very close proximity to one another."

Credit Suisse is betting that because The Cheesecake Factory and Nordstrom often build locations near each other - think the entrances to suburban malls - they will have very similar sales. The same people grabbing a slice of cheesecake often have an opportunity to peruse the racks at Nordstrom in the same trip.

It seems ridiculous, but it actually seems to work.

A regression analysis comparing historical same-store sales data between the companies shows an R-value of 0.93 - the closer to 1, the closer the two match each other. When comparing total sales, the R-value drops slightly to 0.89. (Those values were calculated by Credit Suisse based on historical data through 2013, and just because they were related in the past doesn't mean they will continue to be.)

With online sales increasing for Nordstrom and a holiday shopping spree that affected The Cheesecake Factory but not Nordstrom, the two companies are becoming less correlated.

But for now it's good enough for Exstein.

Nordstrom will report earnings in mid-August, and Credit Suisse is still tracking sales at The Cheesecake Factory to get a read on the retail business' earnings. Exstein rates Nordstrom a "neutral," with a stock-price target about $3 less than the current price of $43.74.

For what it's worth, sales were up at The Cheesecake Factory in the second quarter, but sales growth slowed compared with the first quarter, which could mean bad news for Nordstrom, which has seen shares slide by 17.5% this year.