2x4 in old houses will measure 2x4 and is "rough cut". Modern milling will turn rough cut true 2x4 into the clean cut "2x4" you use today by running them throu

2x4 in old houses will measure 2x4 and is "rough cut". Modern milling will turn rough cut true 2x4 into the clean cut "2x4" you use today by running them through additional planing process. I don't think any shrinkage is significant though. 3/4 plywood will measure less than 3/4.