Philadelphia’s Plastic Bags Ban

From the city’s website:

Philadelphians use almost 1 billion plastic bags each year, which litter our streets, waterways, and commercial corridors. Plastic bags account for over 10,000 hours of lost staff time and pose a danger to workers at recycling facilities because they get caught in the equipment. Banning plastic bags will make our city cleaner, reduce waste and save money.

I’ve been reading Millions, Billions, Zillions by Brian Kernighan (who is apparently a computer scientist of some renown). It’s a great book ($11 in hardcover from Amazon; link to indie booksellers), and Kernighan’s writing style is as buttery smooth as ever. One of the things he does is encourage back-of-the-envelope math on numbers like the above, when you encounter them. Does it make sense that Philadelphians use 1 billion plastic bags per year?

Philly has about 1.6 million residents. 1 billion divided by 1.6 million is 625 plastic bags per person per year, about 12 bags per person per week, or 1.7 bags per person per day. When I consider how often stores double-bag anything vaguely heavy, that seems plausible. (There’s also the fact that Philly gets many tourists, and in normal times there are many non-residents who commute into the city daily for work. Feel free to bump 1.6 million to a higher number, but for ballpark “does this figure make sense” purposes, I think the Census figure is fine.)

10,000 annual hours of lost staff time is high, but seems plausible too: That’s about 192 hours per week, or about 5 full-time employees.

Thursday, 9 September 2021