WE ARE ALL NEOCONOMIST NOW:

The logic behind a sin tax boils down to simple economics. If the price of a product increases, sales can be expected to decrease. But the end goal of a soda tax isn't simply to cut soda consumption--it's to reduce the health problems associated with sugar. So as the first round of soda taxes gains traction, it's time to ask: Are they working?

The answer is hard to find, because research is limited. And what evidence exists is mostly focused on consumption, not health.

A new study published in the May edition of the journal Economics & Human Biology, for example, explored how a tax on soda played out in Seattle. After adopting a 1.7-cent tax for every ounce of soda at the beginning of 2018, soda prices rose by about 59%--and correspondingly, sales fell by 30.5%. Similarly, a study published this week found that a penny-per-ounce soda tax passed (and repealed four months later) in Cook County, Illinois decreased purchases of sugary drinks by 21%. In Philadelphia, soda sales reportedly fell 46%.

Alone, those numbers don't tell you the soda tax caused the drop in drinking: Market data suggest people are voluntarily choosing other drinks over soda, particularly water. But having a tax in place does appear to encourage the switch. Compare Seattle to Portland, which does not have a tax: In the same time period after January 2018, the researchers found sugary drink sales in Portland only dropped by 10% compared to Seattle's 30.5%.

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