Have "the times changed" in the last few decades? Or has this sort of thing being going on for a long, long time? If it has changed, why did it? Was it the independence of women having greater earning power? Or was it social acceptance of female sexuality? Something to do with the availability of birth control and/or good health beyond menopause? How would one design a study to answer those questions?

Older white women join Kenya's sex tourists:

MOMBASA, Kenya (Reuters) - Bethan, 56, lives in southern England on the same street as best friend Allie, 64.

They are on their first holiday to Kenya, a country they say is "just full of big young boys who like us older girls."

Hard figures are difficult to come by, but local people on the coast estimate that as many as one in five single women visiting from rich countries are in search of sex.

Allie and Bethan -- who both declined to give their full names -- said they planned to spend a whole month touring Kenya's palm-fringed beaches.

[...]

"It's not love, obviously. I didn't come here looking for a husband," Bethan said over a pounding beat from the speakers.

"It's a social arrangement. I buy him a nice shirt and we go out for dinner. For as long as he stays with me he doesn't pay for anything, and I get what I want -- a good time. How is that different from a man buying a young girl dinner?"

Yeah, I know, the "hard figures are difficult to come by" phrase made me laugh too.