WASHINGTON — People in sunny, outdoorsy states say they are the happiest Americans.

Ranking No. 1 in happiness was Louisiana, but study co-author Andrew J. Oswald urged a bit of caution in that ranking, noting that part of the happiness survey occurred before Hurricane Katrina struck the state.

Rounding out the happy five were Hawaii, Florida, Tennessee and Arizona. At the other end of the scale, last in happiness — is New York state. Colorado ranked No. 23.

The happiness ratings were based on a survey of 1.3 million people across the country by the Centers for Disease Control and Prevention. It used data collected over four years that included a question asking people how satisfied they are with their lives.

Economists Oswald of the University of Warwick in England and Stephen Wu of Hamilton College in Clinton, N.Y., compared the happiness ranking with studies that rated states on criteria ranging from availability of public land to commuting time to local taxes.

Probably not surprisingly, their report Friday in the journal Science found the happiest people tend to live in the states that do well in quality- of-life studies.

Oswald said “this is the first objective validation of ‘happiness’ data,” which is something he said economists have been reluctant to use in the past.