A blizzard is about to hit DC.  As reports of its magnitude spread yesterday, people unsurprisingly rushed to grocery stores to stock up.  Stores unsurprisingly failed to raise prices to cope with this sudden demand shock.  By the time I got to the grocery store last night around 11 PM, many of the shelves were unsurprisingly empty.

Many, but not all.  They were out of milk and bread, but there was still plenty of cheese and chocolate.  That was easily explained – people knew they could shop again in a few days, so they only needed to stock up on staples.  But the more I looked around, the more puzzled I was.

Here’s what I noticed: For any given type of product, the most popular brand always sold out first.  There were no Eggo waffles, but plenty of Wegmans brand waffles.  All the national brands of hot dogs and sausages were gone, but there were plenty of obscure sausages still on the shelves.  If you broadened the categories, the pattern remained.  In produce, all the bananas were gone, but there were still plenty of apples.

You might say, “What’s the puzzle?  Of course the most popular stuff sells out first.”  But that’s a feeble explanation.  After all, if X is ten times more popular than Y, then you’d expect stores to simply carry ten times as much X as Y.  Why would X sell out faster in a blizzard if stores have already taken its greater popularity into account?