How to avoid unstable markets

Let's put the solution out there and cause upheaval, so that the persons unable to come to terms with the reason behind this proposal quit reading before their economical knee-jerk reactions cause them harm:

Every stock, stock option or secundary investment vehicle when purchased, has to be owned for at least a year.

But...! I know. Don't worry.

But this will make it much harder for companies to raise money! Existing companies will not find difficulties attracting money if they are running a sound business. It will be harder for highly improbable and hypothetical start-ups, yes. Venture capitalists, however, tend to invest for much longer then a year into companies that are unlisted.

But given the amount of transactions made on a daily basis it's nothing but a practical impossibility to keep track of who owns what for how long!
But, then again, the number of transactions will change enormously. Since stocks are no longer owned for split seconds... you get the math?

But if volume declines so steeply, price fluctuations will actually increase! Or, more likely, prices will be a lot more stable, as rumour and massive sell-offs will become much less likely. There will be no automated sell-offs, less possibility for panic, thus no more flash-crashes and a lot less crisis. Cheap deals will still get picked up. But no longer will people with the right instruments be able to leech off of small fluctuations in share prices, at the expense of others that buy and sell. They do not create value on those transactions.

But then how will bankers, short-sellers and the other leeches on the real economy make money? They will probably engage in what by this very action will rightly be denounced as crime, arrested and go behind bars.