[numpad0]

I don't get how reduced UV exposure is supposed to be more attributable to sunscreens than to office labors.

Most industrial materials block roughly 100% of UV rays, except viewing windows which allows as much as 1%. Therefore, just staying in any modern building alone cuts down UV exposure by 99% at very least. There is absolutely no way some translucent face painting does that.

[derefr]

People have been working white-collar jobs indoors behind UV-reflective windows for 50+ years now. Birth-rate decline — especially to below-replacement levels — begins much more recently than that; and is only happening in certain countries.

The set of countries experiencing birth-rate decline is not 1:1 correlated with the set of countries with high/increasing white-collar employment; but, AFAICT, it is 1:1 correlated with the set of countries that have strong avoidance of tanning / strong interest in skin-whitening.

[whyoh]

>but, AFAICT, it is 1:1 correlated with the set of countries that have strong avoidance of tanning / strong interest in skin-whitening.

I'm not seeing that. The countries that are most into avoidance of tanning are probably in Southern Asia, or Asia in general. Their birth rates are not that low, with the exception of Japan, S. Korea and Taiwan.

[derefr]

The middle-class urban populations of these countries really liking lighter skin doesn't imply that the country as a whole will have light skin, though. Achieving that also requires that most of the country be middle-class and urban — being in the set of people who both have time to take care of their skin, and don't spend all day working outdoors in the sun in a way which will unavoidably result in tanning no matter how much sunscreen they use. This is true in Japan / South Korea / Taiwan; but not in these other countries, yet.

You can see it happening in China right now (which also culturally has a preference for lighter skin), as the last few decades of infrastructure build-up have led to a new generation whose parents are lower-class farmers but who are themselves middle-class white-collar workers. My hypothesis would predict a lower birth-rate among this cohort, while the previous generation's birth rate remains high.

[dekervin]

Here is the evolution of the share of blue collar/white collar jobs [0] vs the evolution of fertility rate [1]. I am curious to hear your conclusions from that !

[0] https://publishing.cdlib.org/ucpressebooks/view?docId=ft1580...

[1] https://www.researchgate.net/figure/Historical-Trend-in-US-T...

[bruce343434]

Isn't it a common phenomenon that smarter people have fewer children? Once you achieve high education people are more strategic about when, or if, to have children and how many.

[csdvrx]

> There is absolutely no way some translucent face painting does that.

Wow what a dismissive comment to chemistry and cosmetics.

Just for fun, try take a pic of yourself with a UV camera (or just UV light with some phones), and you'll see it's translucent only to the visible spectrum: https://petapixel.com/2016/05/26/tiny-uv-camera-shows-youve-...

[derefr]

One thing I've recently become curious about, is whether the "UV pigments" in sunscreens are color-fast or not; i.e. whether getting sunscreen on clothing gradually tints the clothing darker when seen in ultraviolet, in the same way that getting throwing a non-colorfast red shirt in with your whites will gradually tint them red.

[numpad0]

The Sun Protection Factor(SPF) is defined "a measure of the fraction of sunburn-producing UV rays that reach the skin" when applied as instructed and only over a defined period, usually 2hr[1]. That means there is twofold difference even between a pane of glass(<1% whole body) and correctly applied sunscreen(~2% for 2hr @ SPF50), before taking walls into accounts.

1: https://en.wikipedia.org/wiki/Sunscreen#Sun_protection_facto...

[LorenPechtel]

This. Note that even single-layer garments generally don't have a protection factor of 100. Simply being outside in warm weather will give you more UV even if you use sunscreen perfectly--and I don't believe perfect use of sunscreen happens in the real world. I don't care how well you apply it, the protection will be degraded by movement. It will be degraded even more by touching things.