There are a few studies that show that the richer you are the better your investment returns - Thomas Piketty the French economist is probably the most well-known author in this space.
A recent Vox article digs into these returns using detailed Swedish data and essentially finds the same thing. The top 5-10% of households do 2.7% per year better than the median, the top 0.5-1% do 4.1% per year higher than the median and the top 0.01% do 6.2% per year better.
But the detail is where it gets interesting,
and confirms Piketty's suggestions - the return can be explained by the asset allocation. Basically, the richer you are the more risky assets you hold and so the higher the returns - especially at the pointiest end where significant private companies are owned.
So, if you are trying to make it onto the rich list the good news is that there is no sign that the rich have some stock-picking secret - on average they get the same returns as most investors, they just take more risk. The bad news (if you are trying to make it onto the rich list) is that the really high returns are usually if you are the founder (or inheritor) of a private company - just dialling up the risk on the stock market is unlikely to get you there.
