Wall Street: What would happen to economy if every broker investes in the right stocks and makes money and no broker invests in the wrong stocks and loses money?

At that point, brokers become irrelevant.  The market is perfectly efficient, and everybody's performance matches the actual profits of the underlying companies profits.  "Beating the market" becomes impossible. World peace and an end to poverty will happen way before this does.

I disagree with the answers here that say the premise is impossible. It IS theoretically possible for money to be invested "correctly."   Abishek Gupta says, "for some to invest (buy) in a stock, someone else has to de-invest (sell)." This is true for established concerns, but there is also the situation of new investments. Suppose there is a new company with a really good idea, like Alexander Graham Bell had in 1876. The purpose of the market is for that company to find investors who will take it from $0 to a number sufficient to capitalize and develop. Nobody sells.   It isn't always easy to pick winners, of course. But it isn't impossible, either. During the '80s BetaMax and VHS both went onto the market and VHS won. But it would have been possible to keep them both in the laboratory until it became clear which was better.   The question asks, "What would happen?" I don't know all that would happen. Presumably the cost of borrowed money would go down as the risk became less. Certainly there would be less trading, if money shifted only when information about investments became convincing. There wouldn't be any short-term profit-taking based on the "greater fool principle." I also suppose more good ideas would get brought to market. It is common wisdom that there are more good ideas than money to develop them. If all investments were good we could begin to see how true that truism is.

That's not possible. Simply because for some to invest (buy) in a stock, someone else has to de-invest (sell) Profits happen if the stock is a one way road, i.e. upwards. In case of derivatives it's always zero sum game. Ones loss is someone else's gain

Impossible

That is great, will go up

The stock market would quickly come to look like the high-quality part of the bond market. That is, no matter what you buy today, $1000 of stock today would be worth about $1030 a year from now. The economy would be better because people would be investing less money in dead ends (buildings and factories in the wrong place that make the wrong stuff; new technologies that don't work), which would mean more investment in useful stuff.

That would mean we are living in a world that is perfectly certain.  There would be of course, zero mistakes, zero waste and all bonds would be rated exactly the same because none of them would ever default.  It would also mean that it would be very easy to start a business because the brokers would know whether or not your business would succeed and you would be able to get instant funding with minimal analysis.

Stock Market is a zero number game. Somebody's win essentially means somebody loss. Speculation is the gas on which the stock markets run. The bears, pessimists of the lot, expect the markets to go down that's why sell..the bulls, optimists of the lot, expect the markets to go up and buy. Bulls losses are bears success stories and vice versa. If the market becomes efficient, ironically there will be no market.