California's Greek Tragedy

I was reading a recent article in the Wall Street Journal entitled "California's Greek Tragedy" and ran across this shocking statistic:

From the mid-1980s to 2005, California's population grew by 10 million, while Medicaid recipients soared by seven million; tax filers paying income taxes rose by just 150,000; and the prison population swelled by 115,000.

I first thought that this might have been a typo.  After all, how is it possible that California could add 10 million people, yet only have an increase in taxpayers of just 150,000?  To date, no retraction or correction has been made to the article.  This statistic is another stark reminder of California's fiscal woes.