What time period is used by yahoo finance to calculate beta
Citing the Yahoo Finance Help page, Beta: The Beta used is Beta of Equity. Beta is the monthly price   change of a particular company relative to the monthly price change of   the S&P500. The time period for Beta is 3 years (36 months) when   available. Regarding customised time periods, I do not think so.
The major drawback to borrowing to invest (i.e. using leverage) is that your return on investment must be high enough to overcome the cost of finance. The average return on the S&P 500 is about 9.8% (from CNBC) a typical unsecured personal loan will have an interest rate of around 18-36% APR (from NerdWallet). This means that on average you will be paying more interest than you are receiving in returns so are losing money on the margin investment. Sometimes the S&P falls and over those periods you would be paying out interest having lost money so will have a negative return! You may have better credit and so be able to get a lower rate but I don't know your loan terms currently. Secured loans, such as remortgaging your house, will have lower costs but come with more life changing risks. The above assumes that you are getting financing by directly borrowing money, however, it is also possible to trade on margin. This is where you post a proportion of the value that you wish to trade with as collateral against a loan to buy the security. This form of finance is normally used by day traders and other short term holders of stocks. Although the financing costs here are low (I am not charged an interest rate on intraday margin trading) there are very high costs if you exceed the term of the loan. An example is that I am charged a fee if I hold a position overnight and my profits and losses are crystallised at that time. If I am in a losing position at that time the crystallisation process and fee can result in not having enough margin to recover the position and the loss of a potentially profit making position. Additionally if the amount of collateral cash (margin) posted is insufficient to cover the expected losses as calculated by your broker they will initiate a margin call asking for more collateral money. If you do not (or cannot) post this extra margin your losing position will be cashed out and you will take as a loss the total loss at that time. Since the market can change very rapidly, such as in a flash crash, this can result in your losing more money than you had in the first place. As this is essentially a loan you can be bankrupted by this. Overall using leverage to invest magnifies your potential profits but it also magnifies your potential losses. In many cases this magnification could be sufficient to lose you more money than you had originally invested. In addition to magnification you need to consider the cost of finance and that your return over the course of the loan needs to be higher than your cost of finance as well as inflation and other opportunity costs of capital. The S&P 500 is a relatively low volatility market in general so is unlikely to return losses in any given period that will mean that leverage of 1.25 times will take you into losses beyond your own capital investment but it is not impossible. The low level of risk automatically means that your returns are lower and so your cost of capital is likely to be a large proportion of your returns and your returns may not completely cover the cost of capital even when you are making money. The key thing if you are going to trade or invest on leverage is to understand the terms and costs of your leverage and discount them from any returns that you receive before declaring to yourself that you are profitable. It is even more important than usual to know how your positions are doing and whether you are covering your cost of capital when using leverage. It is also very important to know the terms of your leverage in detail, especially what will happen when and if your credit runs out for whatever reason be it the end of the financing period (the length of the loan) or your leverage ratio gets too high. You should also be aware of the costs of closing out the loan early should you need to do so and how to factor that into your investing decisions. I work as an investment risk manager for what would popularly be called a top tier investment manager. Most large asset managers use vendor models like RiskMetrics, Algorithmics, Barclays Point, Barra or something similar, and use those to calculate endless varieties of analytics and risk metrics.   Some of these are granular risk models (single asset based and computing covariances between them) while others are factor models (e.g. mapping bonds to a yield curve and sector and country spread and computing the risk largely based on that mapping). Things like Value at Risk in any of its many flavors (simulated vs non simulated, mainly), ex-ante risk relative to a benchmark, stress tests, duration, beta, yield, spread, expected shortfall, what have you...   Counterparty/credit risk is a whole different world I could get into. What else do you want to know in detail? "Calculating beta is finding the correlation between the dependent variable, MSCI world benchmark, and the independent variable, your companies. If you know how to run liner regression models, run each company as the independent variable with the dependent MSCI. You can use Excel to gather this result (Y = MSCI price change at closing hour while X = company stock price closing prince). Running the regression will give you the Beta (and alpha when doing portfolios); which (from linear algebra) is the ""m"" in y = mx + b" First off, great job on your finances so far. You are off on the right foot and have some sense of planning for the future.  Also, it is a great question.   First, I agree with @littleadv. Take advantage of your employer match. Do not drop your 401(k) contributions below that. Also, good job on putting your contributions into the Roth account. Second, I would ask: Are you out of debt?  If not, put all your extra income towards paying off debt, and then you can work your plan. Third, time to do some math.  What will your business look like?  How much capital would you need to get started?  Are there things you can do now on a part-time basis to start this business or prepare you to start the business? Come up with a figure, find some mutual funds that have a low beta, and back out how much money you need to save per month, so you have around that total.  Then you have a figure. e.g. Assume you need $20,000, and you find a fund that has done 8% over the past 20 years.  Then, you would need to save about $110/month to be ready to go in 10 years, or $273/month to go in about 5 years.  (It's a time value of money calculation.) The house is really a long way off, but you could do the same kind of calculation.  I feel that you think your income, and possibly locale, will change dramatically over the next few years.  It might not be bad to double what you are saving for the business, and designate one half for the house. Identify the market and time period. Use the [capital asset pricing model](http://en.wikipedia.org/wiki/Capital_asset_pricing_model) to determine the market beta(http://en.wikipedia.org/wiki/Beta_(finance) for your given stock and interpret the results (if your stock plots above the security market line, it means you are getting higher return for your risk, with consideration of the affects of market risk).  Maybe give a more detailed question? You might simply need to compute a modified [Sharpe Ratio](http://en.wikipedia.org/wiki/Sharpe_ratio) using the market (during the time you've decided is the recession) as the risk free rate. Tough to give a good answer to such a general/non-specific question.  EDIT: link formatting - can't get the beta page to link because of '( )' in url "Calculating beta is finding the correlation between the dependent variable, MSCI world benchmark, and the independent variable, your companies. If you know how to run liner regression models, run each company as the independent variable with the dependent MSCI. You can use Excel to gather this result (Y = MSCI price change at closing hour while X = company stock price closing prince). Running the regression will give you the Beta (and alpha when doing portfolios); which (from linear algebra) is the ""m"" in y = mx + b" Google Finance and Yahoo Finance have been transitioning their API (data interface) over the last 3 months. They are currently unreliable. If you're just interested in historical price data, I would recommend either Quandl or Tiingo (I am not affiliated with either, but I use them as data sources). Both have the same historical data (open, close, high, low, dividends, etc.) on a daily closing for thousands of Ticker symbols. Each service requires you to register and get a unique token. For basic historical data, there is no charge. I've been using both for many months and the data quality has been excellent and API (at least for python) is very easy! If you have an inclination for python software development, you can read about the drama with Google and Yahoo finance at the pandas-datareader group at https://github.com/pydata/pandas-datareader. I can understand if people think I'm showing off. I'm not trying to and I'm extremely sorry if it seems like I am. Trust me, my Beta is probably much larger than it should be relative to my returns. However, I think I can keep the pace up but I just didn't know if this was too short of time to try and make a decision off of or not