American membership in labor unions declined by 767,000 [WORD ILLEGIBLE] per cent, over the past two years, its first drop in 15 years, according to a report released yesterday by the Labor Department.

Bureau of Labor Statistics analysis said the shrinkage reflected the 1974-75 recession and came [WORDS ILLEGIBLE] areas of manufacturture, construction and jobs held by women.

Unions' share of the total labor force, which has been declined steadily in recent years, dropped from 21.7 per cent in 1974 to 20.1 per cent in 1976.

Total union membership, which had been climbing steadily since [WORD ILLEGIBLE] although at a slower rate than the entire labor force, dropped from [WORD ILLEGIBLE] million in 1974 to 19.4 million in 1977.

Membership in AFL-CIO affiliates dropped from [WORD ILLEGIBLE] million to 16.6 million over the two years, although its share of all union members rose from 78 to 79 per cent.

The report underscored the continuing shift of jobs from manufacturing to services, including government and dramatized the difficulty that unions - with their blue-collar orientation - face in capitalizing on the chance.

The only good news for organized labor in the pre-Labor Day report concerned the continued growth of ban gaining groups representing white-collar and service workers, although many of them are employee associations outside the traditional labor movement.

Employee associations - many of which are behaving more and more like unions - grew by [WORD ILLEGIBLE] to a now peak of a million. Half the gain was registered by the National Education Association, which is now the second largest labor organization after the Teamsters, according to BLS.

Among unions, the Teamsters were supplanted by the American Federation of State, County and Municipal Employees as the most successful recruiter of new member.

Public employee unions and associations grew by 600,000, although federal employee members fell by 100,000. Gains came on the state and local levels, where association members outnumber union-card holders.

Although women represent a minority of union members, about 20 per cent, they constitute a majority of the membership loss: 400,000 of 767,000. Associations pick up 350,000 new women members, or about four-fifths of their total gain. The net loss was 50,000.

BLS analysis said the decline of women in unions may reflect the loss of jobs in the garment trades, electronics and other industries that normally hire women as well as the last-hired, first-fired principle that prevails in seniority systems and is acutely felt by minorities and women during recession-caused layoffs.

Similarly, the recession contributed to the loss of nearly 7000,000 union members in manufacturing between 1974 and 1976, the BLS report said. About 1 million manufacturing jobs union and non-union were lost during that period.

AFL-CIO spokesman Albert J. Zack, acknowledging that the figures were "something of a surprise," said it means "we got a big job ahead of us." He said many unions are "organizing like made just to stay even."

The issue of organization has been a flash point within the AFL-CIO, with some internal critics charging that the federation and its affiliates have done too little to recruit new members.

But Zack said he believes the loss came largely because jobs were disappearing in areas where unions are traditionally strong, "many of them because multinational corporations are exporting jobs to foreign countries." The recession, he said was also a factor in loss of union contruction jobs.

AFL-CIO President George Meany, in a Labor Day message, charged that "many employers are using today's high unemployment rates (now 7.1 per cent) to frighten workers interested in unionization."

Employers have historically used fear of jon loss to frighten workers from joining unions, said Meany, adding that "union-busting and high unemployment have always gone hand in hand."

Meany renewed his appeal for congressional enactment of the Humphrey-Hawkins full-employment bill and the Carter administration's labor law revision package, which would remove what unions regard as many legal impediments to organizing, especially in the South.