People should read how the Forbes 400 list got started. It was extremely difficult to get off the ground. It's hard to know who has the most wealth -- it isn't public information, after all. Those who become wealthy via public markets have their ownership disclosed, so we can place a minimum value on their assets, and as a proxy, their total net worth.
The changes to the list over the decades could be more a function of wealth disclosure, which are mandated by the regulatory requirements of equity markets (e.g., we can all look up Zuckerberg's percentage ownership of Facebook).
The changes to the list over the decades could be more a function of wealth disclosure, which are mandated by the regulatory requirements of equity markets (e.g., we can all look up Zuckerberg's percentage ownership of Facebook).