Oh that... no idea, as I have very little knowledge about carbon itself (my brother is way better in this then I am, so most of my custom carbon stuff is his job
). I guess carbon production, knowledge about laying fibers right way improved through the years. I would say carbon is still carbon, so fibers itself are probably same today as they were 20 years ago, but resin improved and most importantly knowledge of putting fibers right way, combining different fibers to achieve extra stiffness at same, or smaller, weight, is what really makes difference. But that's just my assumption, and I'm sure someone with more knowledge about carbon will tell I'm wrong, and will provide proper reason why it's so