My smart and savvy colleague Shani Hilton has just linked to some new research demonstrating that the District’s nearly two-year-old bag tax has been a success. Allow me to dissent. Well, sorta.

Oh, sure, Shani’s argument seems to have all kinds of “statistics” on its side, demonstrating that the tax has meant fewer plastic bags, and less resulting environmental damage when those bags wind up in vacant lots of endangered rivers. And, yeah, its apparent that many Washingtonian consumers—including me—have developed the habit of taking recyclable bags to the Safeway, thereby avoiding the need to pay the District a nickel for those plastic bags that were once used to haul groceries home.

Less environmental damage, little quality-of-life impact. What’s not to like?

But this argument leaves out one demographic: Those of us who walk our dogs. Once upon a time, there was a drawer in my house featuring a seemingly endless supply of plastic bags—souvenirs from every time I bought a dozen eggs or a pack of gum or just about anything else. Nowadays? The drawer’s contents are limited to the long, skinny, poop-unfriendly plastic bags that carry the daily newspaper to my door.

Oh, sure, I could go out and buy bags. But somehow I keep forgetting: It’s easier to acquire the habit of carrying the reusable bag to the store than it is to get comfortable with buying a sheath of plastic bags to bring home inside it.

I’m sure some smartypants economist could come up with an economic model that reassesses the bag tax based on foregone opportunities to re-use free supermarket bags. Which, to be sure, will probably confirm the results Shani pointed to. In the meantime, I’ll stick with my dwindling supply of Post delivery bags—and will wash my hands after coming home from a walk.