Greenberg: Don't Confuse Mattresses and Housing

NEW YORK ( TheStreet) -- People always want to believe there is a relationship between mattresses and housing.

One reason (and it spotlights a flaw in ETFs): Select Comfort ( SCSS) (which blew up this Wednesday after reporting yet another quarter of horrible results) and Tempur Sealy ( TPX) are among the largest holdings of the XHB housing ETF.

So, naturally people want to extrapolate their performance to housing.

Reality: If there is a relationship, it's merely coincidental.

And that comes straight from the mouth of Tempur Sealy CFO Dale Williams.

He was speaking at a Raymond James investment conference in 2011 when an analyst asked if mattress replacement was tied to housing.

Williams: "You can look at this, the relationship between the two industries ad infinitum. Mattresses wear out. People replace their mattress roughly every 10 years.

"Moving can be an impetus to buy a mattress but it is not a cause. The cause of buying a mattress is the mattress is worn out. Certainly, if you are moving home, it may cause you to think about it and I'm moving to a new house so it's time to get a new mattress. But the reason why you buy a new mattress is because it's worn out. It's not that by building houses or by buying a house you suddenly think I need to buy a mattress."

Case closed. (And now will somebody please remove those two companies from the XHB?!)

--Written by Herb Greenberg.

(Originally published on Real Money's Columnist Conversation on Oct.16 at 6.16 pm EST)

Herb Greenberg, editor of Herb Greenberg's Reality Check, is a contributor to CNBC. He does not own shares, short or trade shares in an individual corporate security.

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