Economists have a saying: The right answer is rarely all or nothing. Case in point: Brookline banning plastic bags altogether because of a small uncovered cost of non-biodegradability (“The bag wars,” Ideas, Nov. 25). Instead of a ban, the optimal solution to the paper vs. plastic debate is for Brookline to tax retailers perhaps a penny on each plastic bag, and then spend that money on conservation measures.

Retailers wouldn't pass the tax on to consumers, since they would still prefer that consumers select plastic bags over the more costly paper bags.

Everybody wins this way: Consumers would get a choice, retailers would save money, and the environment would benefit both directly, because of Brookline's windfall spending on conservation, and indirectly, because far fewer paper bags — which use far more resources than plastic — would get consumed.

Al Lewis

The writer, who previously taught economics at Harvard, is the author of "Why Nobody Believes the Numbers."