With a number of twins in my extended family I have to say that yes, there are more twins than ever. But I also have to say that percentage-wise I really don’t think so. My children have way more first, to say nothing of second, cousins than the average family had when I was growing up. Hence the fact that there are way more twins among them does sound somewhat reasonable.
Also, nowadays maternal, fetal, and infant healthcare are such that more are born, alive, and well, than ever before.
Another cause for the increase in multiples is the vast number of women undergoing fertility treatments – at any age the chance of multiples is way higher when assisted than natural.