You can usually infer quite a lot from income data anyway given that wealth and income tend to be quite closely related. Obviously, there are exceptions but in

You can usually infer quite a lot from income data anyway given that wealth and income tend to be quite closely related. Obviously, there are exceptions but in general there is a strong correlation. Furthermore, Piketty and other researchers have gone to great lengths to get reliable wealth data despite the difficulties. The difficulty of performing these investigations rigorously is why I would prefer to trust studies from professional economists rather than a hot-take from a blog.