Monogamy catching on or can't get any?
85% of New Yorkers between the ages of 18 and 64 years (3.6 million) reported having either no sex partner or 1 sex partner in the past year. Few New Yorkers 18–64 years had 3 or more sex partners in the past year
New York City Community Health Survey

It would be interesting to see the further breakdown between one and zero...