WASHINGTON -- Maryland's largest county took in more revenue than expected in the first year of its shopping bag tax. While the numbers seem to indicate Montgomery County shoppers are not ready to give up their bags, county officials are holding off on any interpretation of the data for at least a few more months.

The county initially estimated it would take in between $1.2 million and $1.3 million in the first year of the 5-cent per bag tax on both paper and plastic bags. By the end of December 2012, the revenue totaled $2.3 million, essentially accounting for 57.7 million bags used last year, said Meo Curtis, manager for the stormwater permit coordination section, which oversees Montgomery County's bag tax and related activities.

Curtis said the original estimate was that Montgomery County consumers used as many as 300 million bags per year, though some felt that the "one bag per person per year" estimate was too high. Those figures would mean an 80 percent drop in paper and plastic bag use in the county last year.

But one of the big problems with measuring the efficacy of bag taxes and bans is the fact that no one is really sure how many bags were being used before the laws went into effect, Curtis said.

Washington has taken the lead in the region, approving a 5-cent fee in 2010. The city claimed a huge drop in bag use in the first year, going from 270 million to about 55 million bags – a drop of about 80 percent. The tax brought in about $1.8 million in fiscal 2011, about half of what officials projected which means less revenue for the District but also indicates a continuing drop in the use of plastic bags.

Neighboring Prince George's County in Maryland is struggling to impose a bag fee of its own. Though it has had support at the county level, any revenue-generating measures must be approved by the General Assembly and the state-level enabling legislation failed last year after some lawmakers raised concerns that it would hurt poorer residents who might be less inclined to buy reusable bags.

Efforts to ban plastics bags or impose a 20-cent per bag tax in nearby Virginia have also failed.

San Francisco pioneered banning plastic bags in the United States with its 2007 law, which includes an exception for biodegradable bags. Last year, Seattle barred the use of single use plastic bags and Los Angeles banned plastic bags from its grocery store check out lanes and instituted a fee for paper bags.