National Bureau of Economic Research figures show a national tax of between 1 and 2.5 cents per ounce of drink would save society $7 billion per year.
Retailers say soft drink sales have dropped by half, but preschool teachers are seeing the tax's benefits.
A new city tax is expected to raise millions annually.
Philadelphia is set to become the first major city to introduce a soda tax.
Mexico is fighting obesity by urging people to drink less soda and more water.
A ballot initiative in Richmond and El Monte proposes a tax on sugar-sweetened drinks. Proponents say it could help prevent diabetes among low-income residents and generate revenue, but the soft drink industry is spending millions to block it.
