Apr 6, 2009 5:02 PM EDT Email MainStreet.com (a personal-finance-oriented offshoot of TheStreet.com) just released its Happiness Index , a Prozac-addled tweak on the famous Misery Index . The latter, which combines unemployment and inflation statistics, captured the prevailing worries of the stagflation -prone 1970s; now that inflation has been tamed, MainStreet.com