As long as insider trading has existed, people have been fixated on it. Newspapers give it front page coverage. Cult movies romanticize it. Politicians make or break careers by pillorying, enforcing, and sometimes engaging in it. But, oddly, no one seems to know what's really wrong with insider...

We develop a new methodology to estimate the impact of a financial transaction tax (FTT) on informational efficiency, liquidity and volatility. In our sequential trading model there are price elastic noise traders and traders with private information of heterogeneous quality. We estimate the...