The percentage of Americans behind in their loan payments fell slightly last year as the economy gradually improved, a banking trade group said Wednesday.

The American Bankers Association said the percentage of consumer loans at least 30 days overdue fell to a seasonally adjusted 2.43 percent at the end of the October-December quarter, down from 2.58 percent a year earlier.The quarterly decline was the third straight. The delinquency ratio, which had risen to 2.75 percent during the January-March quarter, fell to 2.60 percent at the end of the next quarter and to 2.46 percent at the end of the third.

"Clearly, 1992 was a better year for the majority of households, although the economy bumped and rolled along," said James Chessen, the association's chief economist.

"These delinquency numbers suggest that consumers' efforts to pay off excessive debt levels during the past two years are finally bearing fruit," he added. "We are optimistic for 1993, especially given lower interest rates on everything from mortgages to credit cards."

Areas of New England, one of the regions hit hardest by the recession, had the highest delinquency rates as 1992 ended. They included New York, 5.26 percent; Rhode Island, 4.80 percent; Connecticut, 4.72 percent; New Hampshire, 4.61 percent; and Massachusetts, 4.46 percent.

Florida reported the lowest delinquency rate, 0.75 percent, followed by South Carolina, 1.18 percent; and Nebraska, 1.35 percent.

The delinquency rate is derived from a survey of 800 banks in the 50 states, the District of Columbia and Puerto Rico. It is a composite of rates for seven types of closed-end consumer loans; two types of auto loans, personal loans, recreational vehicle loans, mobile home loans, property improvement loans and second mortgages.