The share of elderly Americans, especially women, continuing to live independently after losing their spouse has increased sharply.

Some 70 percent of elderly widows lived by themselves in 1997, up from 56 percent in 1970, the Census Bureau reported Monday.During the same period, the share of widowers living by themselves increased from 53 percent to 60 percent, Census statistician Terry Lugaila said.

Overall, 46.3 percent of American women over age 65 were widows, down from 54.4 percent in 1970. That change occurred as men began living longer and as more couples divorced, Lugaila noted.

In 1970, just 2.3 percent of elderly women were divorced; that figure now is 7.4 percent. The share of elderly women still living with their husbands has risen from 34 percent to 40 percent.

The changes were disclosed in the Census Bureau's annual update of Americans' "Marital Status and Living Arrangements."

The analysis also found that, for the first time, the number of unmarried couples in America has topped 4 million. The bureau estimated there were 4,130,000 unwed couples as of March 1997, up from 3,958,000 a year earlier.

As young people choose to delay marriage, or to try life as a couple before making the formal commitment, this group has been growing steadily in recent years.

In 1960, there were fewer than a half-million such couples. The total topped 1 million in 1978, passed 2 million in 1986 and reached 3 million in 1991.

Of the unwed couples, 1,470,000, or about 36 percent, had a child under age 15.