A national tax on sodas and sugary drinks could benefit public health, a new analysis from Berkeley suggests. "What we're trying to do is evaluate whether soda taxes are good or bad overall for society," says assistant economics professor Dmitry Taubinsky, one of the study's co-authors. Along with other economists from the University of Pennsylvania and New York University, the team looked at several factors, including tax revenues, health outcomes, effect on health-care costs, the impact of soda taxes on low-income residents, as well as the pleasure people derive from the drinks, which makes them likely to drink it even when they know it's not good for them. Their cost-benefit analysis suggests that the optimal federal tax would be between 1 and 2.1 cents per ounce. The national tax is recommended so that people can't leave one area with the tax, such as Philadelphia, to buy the drinks in another -- untaxed -- area. "The issue is just that if Philadelphia imposes a soda tax but the neighboring cities do not, then people might engage in cross-border shopping," Professor Taubinsky says. "That is why we also think that instead of implementing taxes in a piecemeal city-by-city basis, it would be best if we did them larger-scale, at a state level or, even better, at a national level."