If you're talking about width as you stated in the thread title, I'm fairly certain older bars are narrower than modern bars. I have a couple of bars from 70/80s bikes that measure 38cm or similar, and my modern bars measure 44cm or similar. You can find newer style bars in narrower sizes, but they're less common and you'll likely have to order new if you want them. As for the flat of the bars to front of curve measurements, that seems to have decreased as well for popular bar styles. It keeps a more consistent posture/stretch when switching between bar positions.