When did a 4X4 become a 3-1/2 X 3-1/2? and how long will it take for a 3-1/2 X 3-1/2 to become a 3X3? and when it does...... and you know it will, will they still call it a 4X4, or even a 3-1/2 X 3-1/2? or will they fess up and call it a 3X3?
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The source says it probably started in the 1870's, but numerous dates since have steadily "justified" the downsizing, from the war effort, to cost of shipping being less for slightly smaller sizes, all kinds of gimmicks and justifications.
Just like the cereal boxes not being full, and the steady reduction in sizes of everything at the local market, but the prices they charge never go down. Makes one wonder if the whole house of cards will collapse someday when plans approved for a house in one era can no longer be safely made because of the thinner wood.
Philomel
4X4's were full size and still are if you want rough sawn lumber.The 1/4" per side loss is on finished lumber unless you buy full 16x16/4( 16 quarters finished lumber) which is a full finished 4X4 but you will pay for it.