Just check out these two quotes and make your own mind up:
"Eskridge and Spedale want to blame the substantial acceleration in Dutch out-of-wedlock birthrates entirely on the opening up of registered partnerships to both gay, and especially straight, couples in 1997." - Stanley Kurtz, on NRO's Corner today.
"The nonmarital birth rate in the Netherlands has been increasing exponentially since the 1970s. It galloped up in the 1980s, and continued that gallop in the 1990s and the new millennium. The rate doubled between 1982 and 1988, doubled again between 1988 and 1997, and is on the way to another doubling. These are significant increases, but registered partnerships, not to mention same-sex marriage, came right in the middle of this demographic trend. Neither institution seems to have exacerbated the trend," - Bill Eskridge and Darren Spedale, in the posting he's "responding" to.