If consumers account for two-thirds of the U.S. gross domestic product, as generally reported, the prospects for continued economic weakness look very real – and maybe even that other R word, recessionary – when you look at share prices of major retail stocks recently.

Banks and building and some other sectors of the stock market haven’t done so well lately either, but the showing of the major big-box retailers seems especially ominous after another rough day Friday considering the clout consumer spending is supposed to have on the economy. Perhaps it’s the higher prices for energy or food or the tightening credit market or the loss of jobs or some other factor that’s finally catching up with consumers. Look at what’s happening to the value of these stocks:

 Kohl’s (KSS), which closed at 47.58 Friday, hasn’t been below 50 since the spring of 2006.
 Target (TGT), which closed at 56.19, is also at its lowest level since 2006 after a July high above 70.
 Sears Holdings (SHLD) sank Friday to 120.87, also its lowest level since 2006.
 Home Depot (HD) has fallen to its lowest level since 2003.
 Wal Mart Stores (WMT) is threatening to drop below 42 to its lowest price since 1999 – now that’s rolling back prices, as their television ads tout.
 Even Nordstrom (JWN), at the other end of the economic spectrum from Wal Mart, has seen its shares fall from near 60 early this year to about half that, going back to lows from mid-2005.

There may be a variety of reasons to explain the setbacks in these stocks, but we are now at the most critical season of the year for most of these retailers. If consumers don’t step up . . . well, let’s just say it could be a pretty bleak holiday for stock index bulls.