The downward trend in sex is directly due to the despair quotient.
Explain to me why birth rates are so high in extremely poor, third world nations where despair and starvation are a way of life? I submit that, without rights, women are chattel and used for sex without regard for pregnancy. Because men are assh*les.
You, on the other hand submit that the United States and other wealthy nations have declining birthrates because people are so miserable they don't have sex? Wealth really sucks, eh?
Once you give women control over their bodies and their pregnancies(and their lives) you immediately see declines in birth rates...