In passing the law without making it specific to gays, however, France distinguished itself from other European countries that have approved civil unions or even marriage for same-sex couples. As a result of that ambiguity, the PACS broadened into an increasingly popular third option for heterosexual couples, who readily cite its appeal: It has the air of social independence associated with the time-honored arrangement that the French call the “free union” but with major financial and other advantages. It is also far easier to get out of than marriage.

The number of PACS celebrated in France, both gay and heterosexual unions, has grown from 6,000 in its first year of operation in 1999 to more than 140,000 in 2008, according to official statistics. For every two marriages in France, a PACS is celebrated, the statistics show, making a total of half a million PACSed couples, and the number is rising steadily.