How much do the Americans' tweets reveal about their relative "happiness"? A great deal, according to a new study conducted jointly by Harvard Medical School and researchers from Northeastern University. Analyzing 300 million Twitter messages Americans posted around the clock from 2006 to 2009, the researchers tracked the incidence of upbeat words such as "love," "glad" and "joy" (versus presumably miserable words such as "mildew" and "umbrella") — and concluded that West Coasters issued a significantly higher number of "happy" tweets than those from other regions. (See video below.) What a "treasure trove" of information, says Nick Bilton in The New York Times. Who knew that our "unhappiest moments" as a nation are on "Thursday evenings, before the last day of the workweek." Hmmm, says Claire O'Neill at NPR. "I've always wanted to move to California. Now I can justify it." Watch a time-lapse video tracking moods across the country over the course of a typical day (the fluctuating size of states are based on the number of tweets originating from them as the day passes):