The U.S. Life Evaluation, a measure of how adults rate their well-being, has climbed back to near its all-time high after tumbling in 2011, Gallup Inc. said. The life rating index, which Gallup and Healthways have been conducting since January 2008, found that Americans rated their lives better in January than in any other month since March 2010. The index rose to 50.1 in January from 48.4 in December, Gallup said. The rating has been climbing steadily since October, when it was 46.8 -- its lowest level in more than two years. It had reached a high mark of 51 in January 2011, but then started steadily sinking in the summer and fall, at the same time that economic confidence tumbled and Americans became more pessimistic about their personal finances. The index is now almost back to its all-time high level and remains far higher than it was amid the 2008 and 2009 economic crisis. The Life Evaluation Index, part of the Gallup-Healthways Well-Being Index, classifies Americans as "thriving," "struggling," or "suffering" -- depending on how they rate their current and future lives on a ladder scale with steps numbered from 0 to 10 based on the Cantril Self-Anchoring Striving Scale. The overall Life Evaluation Index score is calculated by subtracting the percentage of suffering Americans from the percentage of thriving Americans. Results are based on telephone interviews conducted as part of the Gallup-Healthways Well-Being Index survey Jan. 1-31 involving 30,351 U.S. adults. The rating has a margin of error of 1 percentage point.