How far can tax policies go in reducing society's use of plastic shopping bags? Consumers in Ireland have a story to tell.

Ireland introduced a plastic bag tax in 2002, and consumers rapidly cut their average use of plastic shopping bags from 328 to 21, according to the Independent News.

The Irish government decided last year to raise the tax to further discourage shoppers from buying plastic bags. As a result, usage of plastic shopping bags declined from 120 million in 2006 to 100 million in 2007. But the government collected 22 million euros of plastic bag taxes last year, compared to 18 million euros in 2006. "The taxes end up becoming revenue-raising measures," Labour's Environment spokeswoman Joanna Tuffy was quoted in the report.

Chinese consumers are also paying for their plastic shopping bags. But since they are paying retailers instead of the government, it's hard, if not impossible, to find out the nationwide spending on plastic bags. Plus, the money raised in China probably won't be used for eco-friendly purposes, unlike the Irish program. The Irish government, however, is unable to provide a specific breakdown of the use of the plastic bag tax funds because they are mixed in with funds from the landfill levy.