I honestly have no idea if this pie chart is fact or fiction!

I can’t speak to the data, but remember that back in those days there were IBM PCs and then there were “clones.” There was probably a decade where things like reverse engineering firmware and touting compatibility and so on was a huge thing. “IBM” here might not cover Packard Bell, Compaq, Dell, Radio Shack… I can’t remember who was in the business at the time, but it was a big market.

IBM decided to get into the PC market and was playing catch-up, so it decided to use off the shelf parts and license an existing operating system, which opened the door to clones. They still had a pretty good run, especially in the business sector where they were a known quantity (“No one ever got fired for buying IBM”), but had a lot of competition from other manufacturers that really cut into their sales.

Apple kept their systems proprietary, so had fewer overall sales than the PC market as a whole, but had more control over both the user experience and the technology itself.