Quote from rolegario:
Not sure if this necessarily true. The pre-earnings swing play is a classic example. Before it became conventional wisdom, professional traders were making a fortune buying a couple of weeks before earnings and selling just before or after the release. But, as more people learned of the strategy, traders began selling increasingly ahead of the earnings release until the pattern gradually lost it's persistency.
I personally have come up with some equity trading strategies that when played out as small bets, would work out well. However, if multiple players jumped in making the same play, I can definitely see the returns dwindle significantly (for this reason I'm not giving any specifics!).
I'm sure there's something in game, arbitrage, or efficient market theory that would mathematically pan this out.
Anyway, don't mean to beat a dead horse. Despite the postings of several optimists, I think the poll results are gradually telling the true story.
There are a lot of threads discussing the value of sharing winning ideas that allow 'inefficiencies' to be exploited. One really heated one was by Vladiator if you want to check that out.
There's one thing that I've never seen anyone bring up here or in any of my finance classes: The 'dont-share-or it'll get arbitraged away' argument is thrown around as market truth and is assumed to hold always and everywhere. This assumption is based on the premise that all inefficiencies have the same GENERATOR. You brought up the earnings play, as you know there are quite a few of those 'inefficiencies' being arbed away, sure, jan effect, small size whatever.
The generator of the inefficiency was in the case of the earnings play, an extremely simple one, that is the discovery of a tendency towards persistence in trend before the earnings release. Easily detected relationships like that are destined to disappear. IMO, arbitrage strategies like pairs trading and the like performed by the big banks are also weaker strategies in that respect. Sure they might have worked over 10-15 years, but why expect them to persist, especially if ever other quant at every bank is rediscovering them?
However, and here's the crucial point, not all generators are born equal. It is, unreasonable, imho, to claim that the underlying rationales for the various successful technical entry setups are equally robust. Some are less robust than others or downright flimsy, and hence get noticed and washed away. Others remain tried and true over time.
Some of these are robust because of the skewed nature of the distribution of buying and selling power in the market. It's my firm belief that one has to be cynical when approaching the market. The actions of institutions, specialists and market makers leave footprints and if you can read those, you'll understand what I mean. Furthermore, technical setups that are based on human emotions cannot go away. What we have learned from history is that we don't learn from history.And everytime I see a new convert to the random walk religion (insert newly minted MBA fund manager du jour) I am overjoyed and thanking the heavens. That really helps, no kidding.
Of course, we all want to know what those robust inefficiencies are. Let me put it this way: Only the best are drawn to them, the other players, by definition are average and will NEVER catch on. At any point in time there is a given distribution of traders who are losers, just breaking even, making money and those who are really successful. Only those who are in the far right tail of the distribution are in the know, once again by definition.
They could share their strategy with you and that would turn you around assuming you can completely mimic them. Would that kill the golden goose (the generator). No. You would simply joining the small group of winning traders who can rake it in. Only a minority can hack it, only a handful, there can only be so many Tiger Woods, Michael Jordans and Larry Birds. Not everyone will be able to benefit like you for the simple reason that traders are at different stages in their development and have different ABILITIES, just like in sports or life. Not to mention that many of the world's best traders are DISCRETIONARY and while they are disciplined, they are not following rules that can be easily coded in tradestation. Emulating these masters then becomes almost impossible.
The question really is: Do I have what it takes to be in the right tail of the distribution? If you make it there, you will realize that there is absolutely no need to worry about inefficiencies disappearing. You will be in the know, and in the zone.
And no one will be able to take that from you.
Hope this helps,
Maverick.