Statistics, weather, roulette...

Casa Crowndot is within the portion of California currently classified as in stage D4 drought.  This is defined by the indices as occurring 2% of the time or less.  [The picture of the highway alert sign is stolen from KQED.]

I heard this referred to on the radio as a "fifty year drought."  Two percent = 1/50 = happening once in fifty years? 

Wait a second.  I remember being in Berkeley in 1977.  Show of hands:  who is old enough to remember the color drought charts in public rest rooms -- "Don't flush until the color matches..." -- anybody?  But the drought of the 70s was less than 50 years ago.  What gives? 

No fair.  Do over.