Efficient markets hypothesis and performance of IPO shares after lock-up period
There are rules that prevent two of the reactive measures you suggest from occurring. First, on the date of and shortly following an IPO, there is no stock available to borrow for shorting. Second, there are no put options available for purchase. At least, none that are listed, of the sort you probably have in mind. In fact, within a day or two of the LinkedIn IPO, most (all?) of the active equity traders I know were bemoaning the fact that they couldn't yet do exactly what you described i.e. buying puts, or finding shares to sell short. There was a great deal of conviction that LinkedIn shares were overpriced, but scant means available to translate that market assessment into an influence of market value. This does not mean that the Efficient Markets Hypothesis is deficient. Equilibrium is reached quickly enough, once the market is able to clear as usual. Who's to say it wasn't priced into the markets, at least to some degree? Without any information on the behaviour of holders pre-expiry, no one can know if they've been shorting the stock in advance of selling on expiry day. And with the float being such a small proportion of the total issuance, there's always the risk of sudden fluctuations picking up big momentum - which could easily explain the 7% drop on expiry day. Add into all this uncertainty, the usual risks of shorting (e.g. limited upside, unlimited downside), and the observed phenomena aren't by any means killer blows of the Efficient Market Hypothesis. That's not to say that such evidence doesn't necessarily exist - just that this isn't it. "That's the way the markets work in THEORY. In actual fact, markets are subject to ""real world"" pressures. That is, there are so many things going on in the market that the end of the ""Lined In"" lock up is just one of many. To produce the result you describe, traders would have to hold cash in reserve for this so-called ""contingency"" to buy at the end of the lock-up. In most cases, they wouldn't want to because of everything else that is going on.  To use a real world analogy, would you want to wait until the last possible moment before going to the bathroom? Or would you go now while you had the chance? That's what the decision about ""holding cash in reserve for a contingency"" is like."
"As a lefty, mixed emotions I guess. On the one hand, I think the criminal-justice system is far more harsh on ""minor"" crime, like some poor guy stealing $500, than crime that really impacts a lot of people and involves much larger sums, for a variety of reasons. So it's sort of interesting to see a white-collar criminal actually being taken seriously for once.  On the other hand, I'm not a fan of the United States's ridiculous obsession with jailing people for long periods of time. In some other countries, 110-year sentences don't even *exist*. In most of Scandinavia, 15-year sentences are the maximum for any crime, with a very rarely invoked exception that allows the police to petition for someone's release to be delayed if they would pose an imminent threat of violence upon release. So in general I'm against locking lots of people up just as revenge, as opposed to because they would pose a real threat if they were not locked up. I would also prefer to look first for alternative arrangements, such as house arrest and monitoring, and reserve prison only for *really* dangerous people where there is absolutely no possible alternative. I'm not sure Stanford really counts in that category.  So it basically boils down to, by the standards of American criminal justice, white-collar crime is greatly under-prosecuted relative to other crime. But the standards of American criminal justice are uncivilized bullshit, and I'm not sure locking up a bunch of white-collar criminals is a good way to make up for the fact that we lock up too many petty criminals, or even people doing things that shouldn't be crimes at all.  The other, somewhat different, issue is that I think we need to go after systemic problems more than random individuals. The system of finance is the real problem." "Working for a lot of startups, I have seen this cycle. Really it has little to do with making the IPO look good because of number of employees, and is more about making the IPO look good because of planning for the future. Many times an IPO is released, it will be valued at $1.00 (made up) and the market will soar and spike. Now stock shares are valued at $3.00. Great. Till after the dust settles a bit, and stocks are valued at $0.85.  This is ""normal"" and good.  It would be better if the stocks ended a little higher than their initial value, but... such is life.  Now the initial value of the stock is made up of basically the value of the company's assets, and employees are part of those assets and its earning power. They are also a liability, but that has less impact on initial value than assets. Sales right after IPO are based on how well a company will do. Part of that is growth. So it looks nicer to say: ""We have 500 employees and have been growing by 20% per month."" than to say ""We have 100 employees"". In other words, before IPO, employees may be hired to make the company look like it is growing. They may be hired because the budget is projected based on expected growth and expected valuation.  After IPO, you get a concrete number. You have your budget. It may be more than you thought, or it may be less. In our example, the real budget (from capital), is only 28% of the entire projected budget, and 85% of the initial value. It's time to make some budget cuts.  Also, normally, there is a period of adjustment, company wide, as a company goes from VC funding, ""here, have as much money as you want"", to ""real world"" funding, with stricter limits and less wiggle room." Only on an accounting basis. The moment they start selling, it would plunge. Take a look at all the small float tech IPOs. Big pop, but once the lockup period ends, it drops 50% as insiders sell. In the end, fundamentals will rule. Facebook managed to unload a quarter of the company at the vastly inflated $38, which is very impressive. The other tech IPOs typically sell less than 10%, because selling more would lead to very low share prices. Remember, these guys are not retail investors selling 100 shares. The ticker shows the price of the last block of shares that was traded, but when someone tries to sell a couple million shares, then it will plunge. "To add to @keshlam's answer slightly a stock's price is made up of several components: the only one of these that is known even remotely accurately at any time is the book value on the day that the accounts are prepared. Even  completed cashflows after the books have been prepared contain some slight unknowns as they may be reversed if stock is returned, for example, or reduced by unforeseen costs.  Future cashflows are based on (amongst other things) how many sales you expect to make in the future for all time. Exercise for the reader: how many iPhone 22s will apple sell in 2029? Even known future cashflows have some risk attached to them; customers may not pay for goods, a supplier may go into liquidation and so need to change its invoicing strategy etc.. Estimating the risk on future cashflows is highly subjective and depends greatly on what the analyst expects the exact economic state of the world will be in the future. Investors have the choice of investing in a risk free instrument (this is usually taken as being modelled by the 10 year US treasury bond) that is guaranteed to give them a return. To invest in anything riskier than the risk free instrument they must be paid a premium over the risk free return that they would get from that. The risk premium is related to how likely they think it is that they will not receive a return higher than that rate. Calculation of that premium is highly subjective; if I know the management of the company well I will be inclined to think that the investment is far less risky (or perhaps riskier...) than someone who does not, for example. Since none of the factors that go into a share price are accurately measurable and many are subjective there is no ""right"" share price at any time, let alone at time of IPO. Each investor will estimate these values differently and so value the shares differently and their trading, based on their ever changing estimates, will move the share price to an indeterminable level. In comments to @keshlam's answer you ask if there is enough information to work out the share price if a company buys out the company before IPO. Dividing the price that this other company paid by the relative ownership structure of the firm would give you an idea of what that company thought that the company was worth at that moment in time and can be used as a surrogate for market price but it will not and cannot accurately represent the market price as other investors will value the firm differently by estimating the criteria above differently and so will move the share price based on their valuation." NYSE and Nasdaq are secondary markets where stocks are bought or sold. The process of creating new stocks via IPO or private placements etc are called Private Market. "Isn't this effectively saying that the market responds principally to itself, and not to either economic fundamentals, or the profitability of the underlying companies.  If so, the market as a ""price discovery mechanism"" is broken, and investors would be wise to do their own research." Yes, there is a delay between when you buy a stock and when you actually take ownership of it.  This is called the settlement period. The settlement period for US equities is T+2 (other markets have different settlement periods), meaning you don't actually become a shareholder of record until 2 business days after you buy.  Conversely, you don't stop being a shareholder of record until 2 business days after you sell. Presumably at some point in the (far) future all public markets will move to same-day changes of ownership, at which point companies will stop making announcements of the form all shareholders of record as of September 22nd and will switch to announcements of the form all shareholders of record as of September 22nd at 13:00 UTC "To answer your question directly..  you can investigate by using google or other means to look up research done in this area.  There's been a bunch of it Here's an example of search terms that returns a wealth of information. effect+of+periodic+rebalancing+on+portfolio+return I'd especially look for stuff that appears to be academic papers etc, and then raid the 'references' section of those.  Look for stuff published in industry journals such as ""Journal of Portfolio Management"" as an example. If you want to try out different models yourself and see what works and what doesn't, this Monte Carlo Simulator might be something you would find useful The basic theory for those that don't know is that various parts of a larger market do not usually move in perfect lockstep, but go through cycles.. one year tech might be hot, the next year it's healthcare.  Or for an international portfolio, one year korea might be doing fantastic only to slow down and have another country perform better the next year.    So the idea of re-balancing is that since these things tend to be cyclic, you can get a higher return if you sell part of a slice that is doing well (e.g. sell at the high) and invest it in one that is not (buy at the low) Because you do this based on some criteria, it helps circumvent the human tendency to 'hold on to a winner too long' (how many times have you heard someone say 'but it's doing so well, why do I want to sell now""? presuming trends will continue and they will 'lose out' on future gains, only to miss the peak and ride the thing down back into mediocrity.)  Depending on the volatility of the specific market, and the various slices, using re balancing can get you a pretty reasonable 'lift' above the market average, for relatively low risk. generally the more volatile the market, (such as say an emerging markets portfolio) the more opportunity for lift. I looked into this myself a number of years back, the concensus I came was that the most effective method was to rebalance based on 'need' rather than time.  Need is defined as one or more of the 'slices' in your portfolio being more than 8% above or below the average.  So you use that as the trigger. How you rebalance depends to some degree on if the portfolio is taxable or not.  If in a tax deferred account, you can simply sell off whatever is above baseline and use it to buy up the stuff that is below.   If you are subject to taxes and don't want to trigger any short term gains, then you may have to be more careful in terms of what you sell.  Alternatively if you are adding funds to the portfolio, you can alter how your distribute the new money coming into the portfolio in order to bring up whatever is below the baseline (which takes a bit more time, but incurs no tax hit)  The other question is how will you slice a given market?  by company size?  by 'sectors' such as tech/finance/industrial/healthcare, by geographic regions?"