Quote from Pekelo:
1. You ASSUME that insider trading always effects the price. It is not the case. A CEO can get ride of quite a few shares without moving the market.
2. For people being in the same direction as the insider trader the insider trading actually helps. So we can make an argument that it could help just as many people as it hurts...
Also, by monitoring big or important shareholders, the market could be made more effective. Now if a CEO is selling suddenly that doesn't necessery mean he knows some bad news maybe he just needs the money. They already have to report such activity...
Sometimes insider traders also screw themselves (thus the info not always reliable or maybe just for the short term). If Martha had kept those shares 6 months longer, she would have made money on her position...
OK, here is a scenario, what is the difference?:
1. CEO sells his stocks at $50 due to upcoming bad news. After earnings report stocks drop $10, you sell with a 10$ loss per share.
2. CEO doesn't sell his stock, after earnings stocks still plumet, you still have a $10 loss.
its not about stock price movement. its about ceos enriching themselves at the expense of the public. its basic fairness.
