The change in bikini etiquette over the past 10 years?

It seems women's attitudes towards bikinis are changing. 10 years ago you could sit on a beach in Europe and probably a quarter of the women would be topless with full brief bottoms. These days the majority of women are wearing thong bikinis but not going topless.

Is there a correlation between toplessness and thongs? Is it tits or ass but never both? What's the logic behind what you wear?
The change in bikini etiquette over the past 10 years?
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