Both Staples and Radio Shack announced store closings this past week. CNN Money offers up a short but highly informative explanation of what’s up with these and other retail store closings. A key point:

Part of the problem for stores is that there is just too much retail space in many markets. There are about 46 square feet of retail space for every man, woman and child in the United States, according to Robin Lewis, CEO of The Robin Report, a retail strategy newsletter. That’s five times the space than in any other country,

“We’ve had overcapacity in this country for a long, long time,” said Lewis. “The economy now has gotten to the point where it is forcing [retailers] to contract.”

So are Amazon and other online retailers to blame for recent store closings? Yes, but only to a degree:

The growth in online sales is simply making problems at some chains more severe, experts say, not causing the problem by itself.

“It is too simple to say this is what Amazon has wrought,” said [Greg Apter, president of Chicago-based Hilco Real Estate]. “But the online business makes the market more saturated. That’s enough to turn what might have been 100 store closings into 120.”