In the six months since New York City health inspectors started giving letter grades to restaurants, 57 percent of the restaurants have received an A.

The city Health Department says the system is forcing restaurants to improve their cleanliness and food safety. But many restaurant owners say the grading system is subjective and unfair.

The letter-grade system has been in effect since July 2010. Eateries that earn less than an A get a chance to bring their grade up before they have to post it in the window.

The Health Department says it has graded 10,000 restaurants so far.

The New York State Restaurant Association said Tuesday that a large percentage of restaurateurs believe the letter grade system is inherently flawed.