Did Mayor Nutter get the soft drink tax right?

According to two studies in the medical journal Health Affairs small taxes on sodas and other sugar sweetened drinks do not have an impact on reducing consumption or the childhood obesity epidemic.

One study led by Roland Sturm, a senior economist at the RAND Corporation in Santa Monica, Calif., found that "existing taxes on soda, which are typically no much higher than 4 percent … do not substantially affect overall levels of soda consumption or obesity rates."

But Sturm and his coauthors from the University of Illinois at Chicago noted that soda taxes might have a greater impact if the money the tax raised were dedicated to obesity prevention efforts, as Mayor Nutter has proposed with his levy. Nutter wants $20 million of the $77 million a year the tax would raise if fully implemented to be used for obesity prevention. And the mayor's proposed tax of 2 cents per ounce, or 40 cents on a 20-ounce bottle of soda, is far larger than the taxes examined in the Sturm study.

Another study published online in Health Affairs researchers led by Jason M. Fletcher, an assistant professor of public health at Yale University in Connecticut, reported that current policies that restrict children's access to vending machines and impose small taxes on soft drinks are not "effective at reducing children's weight."

But Fletcher and his coauthors concluded that more "comprehensive restrictions on access to soft drinks in schools and imposing higher tax rates than are currently in place" might have more of an impact on the obesity epidemic.