My understanding of markets is very limited, and I mostly have a theoretical understanding of issues of these sorts.
Under the Efficient Market Hypothesis, we assume that the stock market reflects a perfect pricing of stocks given publicly available information.
Now, lets say that for some reason you obtain or deduce some information that predicts that a stock is undervalued, and then you purchase the undervalued stocks. And then assume you publicly release the information you've obtained, which then per the EMF, would eventually lead to the stock being priced at a fair value, earning you a profit.
Such an analysis should also work even if your information predicts that a stock is undervalued, considering that you purchase shorts instead.
Under such analysis, you might conclude that it is in the interest of participants to be open with their information, but in practice we see that financial information is kept very secretively, and any leads or tips are rare to come by.
What is wrong with this analysis?