How do I manage my portfolio as stock evaluation criteria evolve?
Don't sell. Ever.  Well almost. A number of studies have shown that buying equal amounts of shares randomly will beat the market long term, and certainly won't do badly.  Starting from this premise then perhaps you can add a tiny bit extra with your skill... maybe, but who knows, you might suck.  Point is when buying you have the wind behind you - a monkey would make money. Selling is a different matter. You have the cost of trading out and back in to something else, only to have changed from one monkey portfolio to the other. If you have skill that covers this cost then yes you should do this - but how confident are you? A few studies have been done on anonymised retail broker accounts and they show the same story.  Retail investors on average lose money on their switches. Even if you believe you have a real edge on the market,  you're strategy still should not just say sell when it drops out of your criteria.  Your criteria are positive indicators. Lack of positive is not a negative indicator.  Sell when you would happily go short the stock.   That is you are really confident it is going down. Otherwise leave it. If your criteria has changed but some of your existing holdings don't meet your new criteria you should eventually liquidate them, because they are not part of your new strategy. However, you don't want to just liquidate them right now if they are currently performing quite well (share price currently uptrending).  One way you could handle this is to place a trailing stop loss on the stocks that don't meet your current criteria and let the market take you out when the stocks have stopped up trending. Unfortunately I believe there is not a good answer to this because it's not a well posed problem.  It sounds like you are looking for a theoretically sound criteria to decide whether to sell or hold.  Such a criteria would take the form of calculating the cost of continuing to hold a stock and comparing it to the transactions cost of replacing it in your portfolio. However, your criteria for stock selection doesn't take this form.  You appear to have some ad hoc rules defining whether you want the stock in your portfolio that provide no way to calculate a cost of having something in your portfolio you don't want or failing to have something you do want.  Criteria for optimally rebalancing a portfolio can't really be more quantitative than the rules that define the portfolio.
Dummy example to explain this. Suppose your portfolio contained just two securities; a thirty year US government bond and a Tesla stock. Both of those position are currently valued at $1mm. The Tesla position however is very volatile with its daily volatility being about 5% (based on the standard deviation of its daily return) whole there bond's daily volatility is 1%. Then the Tesla position is 5/6 of your risk while being only 1/2 of the portfolio.   Now if in month the Tesla stock tanks to half is values then. Then it's risk is half as much as before and so it's total contribution to risk has gone down. If you are going to the frenzy of individual stock picking, like almost everyone initially, I suggest you to write your plan to paper. Like, I want an orthogonal set of assets and limit single investments to 10%. If with such limitations the percentage of brokerage fees rise to unbearable large, you should not invest that way in the first hand.  You may find better to invest in already diversified fund, to skip stupid fees. There are screeners like in morningstar that allow you to see overlapping items in funds but in stocks it becomes trickier and much errorsome. I know you are going to the stock market frenzy, even if you are saying to want to be long-term or contrarian investor, most investors are convex, i.e. they follow their peers, despite it would better to be a concave investor (but as we know it can be hard).  If the last part confused you, fire up a spreadsheet and do a balance. It is a very motivating activity, really. You will immediately notice things important to you, not just to providers such as morningstar, but alert it may take some time. And Bogleheads become to your rescue, ready spreadsheets here. The problem is that short-term trends are really unpredictable.  There is nobody who can accurately predict where a fund (or even moreso, a single stock or bond) is going to move in a few hours, or days or even months. The long-term trends of the entire market, however, are (more or less) predictable.  There is a definite upward bias when you look at time-scales of 5, 10, 20 years and more.  Individual stocks and bonds may crash, and different sectors perform differently from year to year, but the market as a whole has historically always risen over long time scales. Of course, past performance never guarantees future performance.  It is possible that everything could crash and never come back, but history shows that this would be incredibly unlikely.  Which is the entire basis for strategies based on buying and holding (and periodically rebalancing) a portfolio containing funds that cover all market sectors. Now, regarding your 401(k), you know your time horizon.  The laws won't let you withdraw money without penalty until you reach retirement age - this might be 40 years, depending on your current age.  So we're definitely talking long term.  You shouldn't care about where the market goes over a few months if you won't be using the money until 20 years from now. The most important thing for a 401(k) is to choose funds from those available to you that will be as diverse as possible.  The actual allocation strategy is something you will need to work out with a financial advisor, since it will be different for every person.  Once you come up with an appropriate allocation strategy, you will want to buy according to those ratios with every paycheck and rebalance your funds to those ratios whenever they start to drift away.  And review the ratios with your advisor every few years, to keep them aligned with large-scale trends and changes in your life. There is no magic bullet here.   If you want professional management, because you think they know more about entry and exit points for short positions, have more time to monitor a position, etc... (but they might not) try a mutual fund or exchange traded fund that specializes in shorts. Note:  a lot of these may not have done so well, your mileage may vary "I'm searching for a master's thesis topic in equity investment or portfolio management and I'd be grateful if someone could tell me what are the hot ""trends"" going on right now on the market? Any new phenomenons (like the rise of blockchain, etf... but more relate to the equity side) or debates ( the use of the traditional techniques such as Beta to calculate WACC for example ...) ?" About 10 years ago, I used to use MetaStock Trader which was a very sound tool, with a large number of indicators, but it has been a number of years since I have used it, so my comments on it will be out of date. At the time it relied upon me purchasing trading data myself, which is why I switched to Incredible Charts. I currently use Incredible Charts which I have done for a number of years, initially on the free adware service, now on the $10/year for EOD data access. There are quicker levels of data access, which might suit you, but I can't comment on these. It is web-based which is key for me. The data quality is very good and the number of inbuilt indicators is excellent. You can build search routines on the basis of specific indicators which is very effective. I'm looking at VectorVest, as a replacement for (or in addition to) Incredible Charts, as it has very powerful backtesting routines and the ability to run test portfolios with specific buy/sell criteria that can simulate and backtest a number of trading scenarios at the same time. The advantage of all of these is they are not tied to a particular broker. "Fama-French would be a couple of names if you want to look at this from a value/growth dichotomy.  A simplified form of this was to take the stocks with a lower Price/Book Value that would be the value stocks while the others would be the growth.  The principle is that some of the beaten-down stocks will appreciate more than the growth stocks will.  6 Ways To Improve Your Portfolio Returns Today also makes note of the ""growth vs value"" split if you want another reference that way.  Historically, growth has been more volatile and produced lower returns, though past performance isn't necessarily always going to hold as some people like to invest in what is known as a ""slice & dice"" portfolio where a portion in invested in each of 4 corners: Large-growth, large-value, small-growth, and small-value.  Some may add in bonds, REITs, and foreign stocks but the idea is that in different years, different parts of the market will do better and this is a way to capture that in a sense." From Vanguard's Best practices for portfolio rebalancing: Katherine from Betterment here.  I wanted to address your inquiry and another comment regarding our services.  I agree with JAGAnalyst - it's detrimental to your returns and potential for growth if you try to time the market.  That's why Betterment offers customized asset allocation for each portfolio based on the nature of your goal, time horizon, and how much you are able to put towards your investments.  We do this so regardless of what's happening in the markets, you can feel comfortable that your asset allocation plus other determining factors will get you where you need to go, without having to time your investing.  We also put out quite a bit of content regarding market timing and why we think it's an unwise practice.  We believe continuously depositing to your goal, especially through auto-deposits, compounding returns, tax-efficient auto-rebalancing, and reinvesting dividends are the best ways to grow your assets. Let me know if you would like additional information regarding Betterment accounts and our best practices.  I am available at buck@betterment.com and am always happy to speak about Betterment's services. Katherine Buck, Betterment Community Manager it's kind of like a circular loop:  i think he would suggest identifying strategies/portfolio managers who have demonstrated outperformance in a persistent manner.  Thing is, that's also really hard to do.  I think empirically, MPT suffers when the market does. By diversifying, you'll only be down less. He's suggesting shooting for absolute returns -- no matter what the market does, he wants to see positive gains.  (a lot) easier said than done Quick and dirty paper but pretty interesting.. I'm not in Portfolio Management but I probably would have ended up at the modal number as well.   I don't know the subject deeply enough to answer my own question, but is the bias always toward underestimation of variance? Or is that a complex of the way the problem was set up?   Another question I have for those in investment management; Would this impact asset allocation? I'd recommend looking at fundamental analysis as well -- technical analysis seems to be good for buy and sell points, but not for picking what to buy.  You can get better outperformance by buying the right stuff, and it can be surprisingly easy to create a formula that works.  I'd check out Morningstar, AAII, or Equities Lab (fairly complicated but it lets you do technical and fundamental analysis together).  Also read Benjamin Graham, and/or Ken Fisher (they are wildly different, which is why I recommend them both). You can evaluate portfolio raw returns or risk adjusted returns. To evaluate raw returns, I would personally compute the total returns over the time period in question for both portfolios.  To compute total returns, split the time into a bunch of subperiods by the dates at which you contributed money.  Compute each subperiod return by dividing the value of the portfolio at the end of the subperiod (but before adding additional cash on that day) by the value at the beginning of the subperiod (after adding cash on that day).  Then multiply all these returns together.  Finally, subtract 1.  That's your total return. For the portfolio where you didn't add any money it's easy: just divide the end value by the beginning and subtract 1. Whichever has a higher return performed better. To compute risk adjusted returns, get the portfolio returns from both portfolios (daily or monthly) and use OLS to regress on a benchmark portfolio return (something like the S&P500).  The intercept of the regression is a measure of the risk-adjusted peformance of your portfolio.  Higher the better.  More sophisticated models will do multiple regression using a few benchmark portfolios at the same time. Ask yourself a better question: Under my current investment criteria would I buy the stock at this price? If the answer to that question is yes you need to work out at what price you would now sell out of the position. Think of these as totally separate decisions from your original decisions to buy and at what price to sell. If you would buy the stock now if you didn't already hold a position then you should keep that position as if you had sold out at the price that you had originally seen as your take profit level and bought a new position at the current price without incurring the costs. If you would not buy now by those criteria then you should sell out as planned. This is essentially netting off two investing decisions. Something to think about is that the world has changed and if you knew what you know now then you would probably have set your price limit higher. To be disciplined as an investor also means reviewing current positions frequently and without any sympathy for past decisions. "The raw question is as follows:  ""You will be recommending a purposed portfolio to an investment committee (my class). The committee runs a foundation that has an asset base of $4,000,000. The foundations' dual mandates are to (a) preserve capital and (b) to fund $200,000 worth of scholarships. The foundation has a third objective, which is to grow its asset base over time.""   The rest of the assignment lays out the format and headings for the sections of the presentation.  Thanks, by the way - it's an 8 week accelerated course and I've been out sick for two weeks. I've been trying to teach myself this stuff, including the excel calculations for the past few weeks."