Productivity at the nation's private businesses other than farms rose at an annual rate of 1.2 percent in the third quarter, the same rate as in the previous three months, the Labor Department reported yesterday.

Because of a decline in productivity -- a measure of economic efficiency based on the output of goods and services per hour worked -- from a 3.1 percent rate in the first quarter of this year, the third-quarter gain left the level only 0.4 percent higher than it was one year earlier.

In the third quarter, output rose at a 3.2 percent rate, while the number of hours worked went up at a 2 percent rate. Over the year, output was up 2.7 percent and hours worked 2.3 percent, the department said.

Compensation per hour increased at a 3.9 percent rate in the third quarter, up from a revised 3.4 percent rate in the second quarter. Labor costs per unit of output, a major influence on inflation, rose at a 2.7 percent rate in the third quarter. They were up 3.6 percent compared with a year ago.

In manufacturing alone, productivity rose at a 2.4 percent rate, down sharply from a revised 6.8 percent rate in the second quarter. The gain over the past four quarters was 2.2 percent.

Unit labor costs in manufacturing went up at a 0.5 percent rate in the lastest quarter and were up 2.4 percent from a year ago.

In a separate report, the department said major collective bargaining agreements reached during the first nine months of this year provided for annual wage adjustments of 2.3 percent in the first year of the contract.

This was the lowest first-year contract increase since the Labor Department began keeping these statistics in 1962. The report said that over the life of the contract, the settlements called for average annual wage increases of 2.9 percent.

The department's collective bargaining survey covers industries employing 7 million workers in bargaining units with at least 1,000 workers. The last time the same parties bargained, generally two to three years ago, salary increases averaged 3.8 percent for the first year of the contract and 3.4 percent annually over the life of the contract.