And there are statistics tests one can use to determine if one's performance meets those statistical parameters to be random. Many funds and managers beat it over the long term, such as Warren Buffet, but the vast majority indeed do not.
In addition to that, there might be an effect due to the media hype around investments of Warren Buffet. People see in the news that Buffet invested in companyXYZ so they think that must be a smart idea and also invest in the same company and therefore driving the price higher...
