Chart: How Much _____ Could You Eat on a Dollar?

Lapham’s Quarterly put together this graphic showing just how much food a dollar will get you. A buck could net you four eggs, a little more than a half gallon of bottled water, or an entire McDouble sandwich. That's anywhere from zero to 1,080 calories.

It’s a compelling illustration of how unhealthy food can be a lot cheaper than healthy food. And that food price gap, like the income gap, has become even more pronounced over the last four decades, according to David Leonhardt of The New York Times. Now more than ever, you can pick up a lot of calories for very little cash. While the cost of cheeses and meats is dropping, the cost of fruits and veggies is climbing. And over the past 30 years, the price of carbonated soft-drinks has plummeted.

As Robert Paarlberg outlined earlier this year, we can't entirely blame the shift on agricultural subsidies and price supports for corn. The real issue here is that any effort to curb consumption of unhealthy eats runs up against the big business of selling more food. Just think about why the Nutrition Keys label is so insipid.

If manufacturers aren't taking the necessary steps to sell healthier foods, should we start taxing unhealthy foods? After all, cigarette taxes probably played a bigger role in changing smoking behavior than warning labels did. Last year, economic researchers published a review of studies in the American Journal of Public Health estimating that a 10 percent tax on soft drinks would reduce purchases of Cokes and Pepsis by roughly the same percentage. In addition to a soda tax, it's worth making affordable, healthy foods the default option rather than the alternative (although we tend to overeat junk food more than we under-eat vegetables).

In the end, our food choices don't come down to economics alone. But bringing the cost per calorie into focus—in other words, making sure we compare apples to orange soda—could still pay off in the long run.

Chart via Lapham's Quarterly.