Where or how can I model historical market purchases
Robert Shiller has an on-line page with links to download some historical data that may be what you want here. Center for the Research in Security Prices would be my suggestion for another resource here. This site should help you to accomplish what you are looking for: https://www.quantopian.com
I'm kind of shocked that no formal behavioral modeling has been proposed as an explanation yet. One such model would be steep (hyperbolic, quasi-hyperbolic) discounting.  Consumers would rather pay for popcorn later than for an expensive movie ticket now.  For instance, consumers might when purchasing the ticket see a low value of popcorn and view the ticket price as the whole price because they do not predict purchasing popcorn.  Then when entering the theater, the present value of popcorn is very high and they purchase it.  There might therefore be a market for a commitment device (such as a popcornless theater) to make the appropriate decision ex-ante.  Another commitment device that seems to be practiced is when individuals sneak their own popcorn into the theater.  They may not actually want the popcorn, but by bringing their own they ensure they do not purchase the theater's. "I like Muro questions! No, I don't think they do.  Because for me, as a personal finance investor type just trying to save for retirement, they mean nothing. If I cannot tell what the basic business model of a company is, and how that business model is profitable and makes money, then that is a ""no buy"" for me.  If I do understand it, they I can do some more looking into the stock and company and see if I want to purchase. I buy index funds that are indexes of industries and companies I can understand.  I let a fund manager worry about the details, but I get myself in the right ballpark and I use a simple logic test to get there, not the word of a rating agency. If belong in the system as a whole, I could not really say.  I could not possibly do the level of accounting research and other investigation that rating agencies do, so even if the business model is sound I might lose an investment because the company is not an ethical one.  Again, that is the job of my fund manager to determine.  Furthermore and I mitigate that risk by buying indexes instead of individual stock." "A diversified portfolio (such as a 60% stocks / 40% bonds balanced fund) is much more predictable and reliable than an all-stocks portfolio, and the returns are perfectly adequate. The extra returns on 100% stocks vs. 60% are 1.2% per year (historically) according to https://personal.vanguard.com/us/insights/saving-investing/model-portfolio-allocations To get those average higher stock returns, you need to be thinking 20-30 years (even 10 years is too short-term). Over the 20-30 years, you must never panic and go to cash, or you will destroy the higher returns. You must never get discouraged and stop saving, or you will destroy the higher returns. You have to avoid the panic and discouragement despite the likelihood that some 10-year period in your 20-30 years the stock market will go nowhere. You also must never have an emergency or other reason to withdraw money early. If you look at ""dry periods"" in stocks, like 2000 to 2011, a 60/40 portfolio made significant money and stocks went nowhere. A diversified portfolio means that price volatility makes you money (due to rebalancing) while a 100% stocks portfolio means that price volatility is just a lot of stress with no benefit. It's somewhat possible, probably, to predict dry periods in stocks; if I remember the statistics, about 50% of the variability in the market price 10 years out can be explained by normalized market valuation (normalized = adjusted for business cycle and abnormal profit margins). Some funds such as http://hussmanfunds.com/ are completely based on this, though a lot of money managers consider it. With a balanced portfolio and rebalancing, though, you don't have to worry about it very much. In my view, the proper goal is not to beat the market, nor match the market, nor is it to earn the absolute highest possible returns. Instead, the goal is to have the highest chance of financing your non-financial goals (such as retirement, or buying a house). To maximize your chances of supporting your life goals with your financial decisions, predictability is more important than maximized returns. Your results are primarily determined by your savings rate - which realistic investment returns will never compensate for if it's too low. You can certainly make a 40-year projection in which 1.2% difference in returns makes a big difference. But you have to remember that a projection in which value steadily and predictably compounds is not the same as real life, where you could have emergency or emotional factors, where the market will move erratically and might have a big plunge at just the wrong time (end of the 40 years), and so on. If your plan ""relies"" on the extra 1.2% returns then it's not a reasonable plan anyhow, in my opinion, since you can't count on them. So why suffer the stress and extra risk created by an all-stocks portfolio?" "does it mean uncontrolled severe deflation/inflation is more likely to   occur compared to ""normal"" currencies such as USD, EUR etc? Look at the chart referenced in the link in your question.  It took approximately 50 years for annual production of gold to double from 500 tons to 1000 tons.  It took approximately 40 years for annual production to double from 1000 tons to 2000 tons. Compare that to the production of US dollars by the Federal Reserve (see chart below obtained from here).  US dollar production doubled in DAYS.  Which one do you think will lead to uncontrolled inflation/deflation? Update: Why did I include a chart of the FED's balance sheet?  Because this is the way newly printed money is introduced - the FED will purchase something from banks (mortgage-backed securities, US treasuries, etc.) with newly printed money.  The banks can then loan this money to people who then deposit the money into other banks who loan those deposits to other people and so on.  This is how the fractional reserve process expands the money supply.  This is why I did not include a chart of the money supply since that is counting the same money multiple times.  If I deposited 100 newly minted coins into a bank and that bank proceeded to loan out 80 of my coins where 80 are deposited into another bank who then proceeds to loan out 60 of the coins, and so on....the production of coins only changed by the initial 100 that I minted - not by the fractional reserve multiple. There are historical examples of inflation with gold and silver as duff has pointed out.  None of them come close in magnitude to the inflation experienced with government fiat money." You can also use ICS&lt;GO&gt; on Bloomberg and choose the right category (many subcategories, probably you'll start on home builders or something like that). If that doesn't work, press F1 twice and ask it to an analyst. I'm sure they have this info. http://www.euroinvestor.com/exchanges/nasdaq/macromedia-inc/41408/history will work as DumbCoder states, but didn't contain LEHMQ (Lehman Brother's holding company). You can use Yahoo for companies that have declared bankruptcy, such as Lehman Brothers: http://finance.yahoo.com/q/hp?s=LEHMQ&a=08&b=01&c=2008&d=08&e=30&f=2008&g=d but you have to know the symbol of the holding company. Unless you are buying millions of dollars worth of a stock at a time, your transaction is a drop in the bucket, unlikely to have any noticable effect on the stock price. As Ian says, it's more likely that you are just remembering the times when the price dropped after you bought. If you keep careful track, I suspect you will find that the price goes up more often than it goes down, or at least, that the stocks you buy go up as often as the average stock on the market goes up. If you actually kept records and found that's not true, the most likely explanation is bad luck. Or that someone has placed a voodoo curse on you. I suppose one could imagine other scenarios. Like, if you regularly buy stock based on recommendations by well-known market pundits, you could expect to see a temporary increase in price as thousands or millions of people who hear this recommendation rush to buy, and then a few days or weeks later people move on to the next recommendation, the market setttles down, and the price reverts to a more normal level. In that case, if you're on the tail end of the buying rush, you could end up paying a premium. I'm just speculating here, I haven't done a study to find if this actually happens, but it sounds plausible to me. Here's what the GnuCash documentation, 10.5 Tracking Currency Investments (How-To) has to say about bookkeeping for currency exchanges. Essentially, treat all currency conversions in a similar way to investment transactions.  In addition to asset accounts to represent holdings in Currency A and Currency B, have an foreign exchange expenses account and a capital gains/losses account (for each currency, I would imagine).  Represent each foreign exchange purchase as a three-way split: source currency debit, foreign exchange fee debit, and  destination currency credit. Represent each foreign exchange sale as a five-way split: in addition to the receiving currency asset and the exchange fee expense, list the transaction profit in a capital gains account and have two splits against the asset account of the transaction being sold. My problems with this are: I don't know how the profit on a currency sale is calculated (since the amount need not be related to any counterpart currency purchase), and it seems asymmetrical.  I'd welcome an answer that clarifies what the GnuCash documentation is trying to say in section 10.5.