Does New York's "Walking Culture" explain the city's impressive longevity gains?

My freshman statistic class in college started with our professor stating "numbers don't lie, statistics do." He went on to explain that far too often statistics are cited to bolster an argument that is incorrect. One of the biggest and most common errors of influential statistics is in confusing causation with correlation.

This subject came up in a WSJ story questioning the role of walking in adding to the longevity of New Yorkers. From the WSJ: "Since 1990, New York has added 6.2 years to its average life expectancy, while the rest of the country has added 2.5 years."

This has lead some researchers to infer that the gains are (at least partially) the result of the fact that New Yorkers are forced to walk more than other more auto-centric places to live. By walking more, New Yorkers get more exercise and thus live longer, right? Well, maybe.

Some skeptics wonder if cities are such good personal trainers, however. University of Toronto economist Matthew Turner tracked 6,000 Americans over six years, and found that people who moved from dense neighborhoods to suburbia didn't change weight -- an indication, he says, that people who like to walk will move to cities, while people who are less active will gravitate toward suburbia.

No one disputes the benefit and importance of walking but sources of health information, including LifeTwo, need to be diligent about separating cause from correlation. There is enough conflicting health advice without using Excel to create more. Well that's something you can think about as you go for your daily walk.