[highfreq]

I work in sawmill technology. Way back in history 2x4 were cut to 2" x 4". In a modern sawmill 2x4s are never cut to 2" x 4". They are cut to a thickness and width such that given saw deviation, and variable drying shrinkage nearly all boards will cleanly plane down to 1.5" x 3.5". The exact target dimensions will depend on how well the mill can control their saw deviations and the statistical range of shrinkage they expect for the wood they are cutting. Reducing dimension targets by controlling saw deviation and understanding drying shrinkage is a big part of sawmill efficiency and profitability.

[wfleming]

Fair enough, thanks for those details. Out of curiosity, do you know roughly what the target dimensions usually are now a days? I'm curious how much the efficiency gains are.

It's interesting that lumber kind of looks like shrinkflation (what the comment I was originally responding to suggested), but it's more that technical improvements have allowed producing the same finished product with less input material. But we still label the stuff by the amount of input material it used to take for historical reasons, which at a glance looks like shrinkflation.

[bombela]

https://en.m.wikipedia.org/wiki/Lumber

And what's is worse is how hard it is to know the true size of everything you find in stores in the USA. The same applies to pipes of all types. But even things like a drawer slide is often not the advertised length. Saw blades thinkness is converted from 2.5mm to whatever the closest inch the salesperson felt that day.

From having spent quite a lot of time in big box stores in France and the USA. I can tell you that in the USA 3/4" (19mm) can be anything from 16mm to 24mm.

In short almost everything is built in metric and the USA likes to pretend it's not and gets confused by rounding up randomly.