A record low of 51 percent of US adults are married, and Americans are waiting longer than ever to tie the knot, the Pew Research Center said on Wednesday.

The Washington-based Pew Research Center based its findings on an analysis of US Census data for 2010.

The Pew Center's study also found the number of new marriages in the United States dropped 5 percent between 2009 and 2010, and the group said the slow economy could have contributed to that.

By comparison to the current record low of 51 percent of US adults in married relationships, 72 percent were in wedded unions in 1960, the Pew Center said.

The Pew Center also found that the median age at first marriage for brides stands at 26.5 years and for grooms it is 28.7 years. That is the oldest Americans have ever been when first saying their vows.

Researchers noted the United States is not alone in seeing marriage rates fall, and that other advanced, post-industrial societies are seeing the same long-term declines.

The Pew Center said in its report on marriage rates that it is "beyond the scope" of the group's analysis to "explain why marriage has declined".