The $1 billion Mexican food category has grown at a compound rate of 11 percent since 1988 in grocery store, club store and restaurant sales.

Surprisingly, the study also said that restaurant sales increased about 14 percent in some cases when a smoke-free ordinance was in effect.

Americans spent $20 billion on restaurant pizza last year - that added up to 12 percent of all restaurant sales.

Admission to the museums is free, but the institution relies on income from gift shop and restaurant sales.

The company projects that restaurant sales will top $1 billion this year.

But its core business, restaurant sales in the United States, continued to be sluggish.

Among the strongest sectors of the regional economy in recent months have been tourism, restaurant sales and the entertainment industries.

"The presence of a 100 percent smoke-free ordinance had no significant effect on total restaurant sales in any community," the study said.

Originally, in the 1960s, Mövenpick ice cream was produced for restaurant sales only.

But he said he expected the program to lead to "incremental" improvements in restaurant sales.