Fewer than half of the 7.8 million persons unemployed in the first three months of 1977 lived in households in which no one else - such as a spouse or child - had a job, according to new data developed by the Bureau of Labor Statistics.

Of the 7.8 million who were unemployed, 6.7 million lived in families and 1.1 million did not, although even all these persons did not live alone since unrelated individuals living together are not counted as a family for statistical purposes.

The new data, presented in an article in the July Monthly Labor Review by deputy BLS commissioner Janer L. Norwood, indicates that 41.8 per cent of all unemployed individuals were in households in which they were the only wage earner.

In families, only 32.2 per cent of the unemployed were the sole sources of income.

Norwood said that the new BLS data focuses more on the relationship of the individual "to the people with whom they live," than did the old approach. Most BLS data gathering has been concerned with an average family, usually headed by a male who has a wife and two children.

The "average" family is a limited concept today because of the increased numbers of single-parent families and families with more than one wage earner.

Norwood cautions' that the average family is more important "than statistics suggest, because many American families do pass through this stage. Nevertheless, policies dealing with the family must take account of the increasing variety of family types."

She noted that the "number of families with more than one earner is now larger than the number of single-earner families."

Last year there were 15.6 million single-earner families - most of them with the husband the sole wage earner - while there were 19.7 million with two earners and 7.2 million with three or more earners.

The data on the numbers of unemployed persons in families in which they are not the sole source of income seems to bear out what many economists have argued for a while: that the overall unemployment numbers reported each month may overstate economic hardship.

According to the BLS, the unemployment rate for women whose husbands have jobs is 6.4 per cent, while the unemployment rate for women with unemplyed husbands was 13.8 per cent.

Of the 418,000 unemployed women who headed families with no husband present, however, almost 82 per cent were the sole wage earner. There were nearly 2 million unemployed husbands during thefirst quarter, 51.6 per cent of whom were the only wage earner.