Going long vs short, mechanisms involved
My instinct says that there should be no difference. Your instincts are right. Your understanding of math is not so much. You sold $100K at the current price of 7500000RUB, but ended up buying at 3500000, you earned 3500000RUB. That's 100% in USD (50% in RUB). You bought 7500000RUB for the current price of $100K, but sold later for $200K. You earned $100K (100% in USD), which at that time was equal 3500000RUB. You earned 3500000RUB. That's 50% in RUB. So, as your instincts were saying - no difference. The reason percentages are different is because you're coming from different angles. For the first case your currency is RUB, for the second case your currency is USD, and in both cases you earned 100%. If you use the same currency for your calculations, percentages change, but the bottom line - is the same.
"No, because:  (a) People shift industries as wages adjust  (b) people increase their standard of living  Let's take (a).  As stockbreaker points out, most people in the United States were involved with agriculture at, say, 1800 (I dunno about 1900, but that's possible).  Yes, as we mechanized agriculture, we eliminated need for farm workers.  Simultaneously, as a factory worker could produce more *stuff*, the wage ratio became more-and-more favorable to move into factories.  As a result, we saw massive urbanization; instead of people living in the country, they moved to the city and worked in other types of jobs.  In 1700, in, say, England, less than half of the *men* were even literate.  Today, we spend over a decade simply educating people.  Then let's look at (b).  Let's say that you have some company with a couple of software engineers and a couple of business guys that makes huge amounts of money.  Google or something.  What are they going to *do* with that money?  Okay, maybe they don't pull a Bill Gates and just give it away, but seriously, what do they do?  Well, one thing they could do is to just live the life they would have anyway and refuse to spend any more money.  That's possible, but unlikely; people usually want to work for the things that money can buy, not just money.  So they go out and get a Rolex watch (which sends wealth to watch manufacture and marketing people) or a yacht (which sends wealth to boat builders).  Both are very pricey items relative to the benefit someone gets, but there's a degree of diminishing returns.  The money flows on back.  People have been concerned that we'd ""run out of work"" for a long time, as technology improves productivity.  They've proposed that we'd have to have an eight hour work week because there simply wouldn't be demand for the extra labor.  And if we maintained the kind of standard-of-living that people had a few centuries back, then maybe we would have that eight hour work week.  But historically, we've always simply found new things that cost more that soak up more money." "It's a tricky question w/out more context. If your only options are between stock/funds and letting it sit (i.e. in a saving or CD), I'd have to say option one is the way to go (but that's based on my situation, and you did ask ""if you .."").  However, I think the true answer is ""it depends."" It depends on your risk tolerance and what are your short-term vs. long-term financial needs. Only after answering those questions you can then seek to strategize and diversify investment accordingly." "Simplest way to answer this is that on margin, one is using borrowed assets and thus there are strings that come with doing that. Thus, if the amount of equity left gets too low, the broker has a legal obligation to close the position which can be selling purchased shares or buying back borrowed shares depending on if this is a long or short position respectively. Investopedia has an example that they walk through as the call is where you are asked to either put in more money to the account or the position may be closed because the broker wants their money back. What is Maintenance Margin? A maintenance margin is the required   amount of securities an investor must hold in his account if he either   purchases shares on margin, or if he sells shares short. If an   investor's margin balance falls below the set maintenance margin, the   investor would then need to contribute additional funds to the account   or liquidate stocks in the account to bring the account back to the   initial margin requirement. This request is known as a margin call. As discussed previously, the Federal Reserve Board sets the initial   margin requirement (currently at 50%). The Federal Reserve Board also   sets the maintenance margin. The maintenance margin, the amount of   equity an investor needs to hold in his account if he buys stock on   margin or sells shares short, is 25%. Keep in mind, however, that this   25% level is the minimum level set, brokerage firms can increase, but   not decrease this level as they desire. Example: Determining when a margin call would occur. Assume that an   investor had purchased 500 shares of Newco's stock. The shares were   trading at $50 when the transaction was executed. The initial margin   requirement on the account was 70% and the maintenance margin is 30%.   Assume no transaction costs. Determine the price at which the investor   will receive a margin call. Answer: Calculate the price as follows: $50 (1- 0.70) = $21.43 1 - 0.30 A margin call would be received when the price of Newco's stock fell   below $21.43 per share. At that time, the investor would either need   to deposit additional funds or liquidate shares to satisfy the initial   margin requirement. Most people don't want ""Margin Calls"" but stocks may move in unexpected ways and this is where there are mechanisms to limit losses, especially for the brokerage firm that wants to make as much money as possible. Cancel what trade? No, the broker will close the position if the requirement isn't kept. Basically think of this as a way for the broker to get their money back if necessary while following federal rules. This would be selling in a long position or buying in a short sale situation. The Margin Investor walks through an example where an e-mail would be sent and if the requirement isn't met then the position gets exited as per the law." I wish that I could share the same positivity as you, but aerospace is going (I'm a mechanical engineer btw). Boeing has been our biggest airplane producer and the only company to rival airbus, but their production (and design) is being moved to China. https://www.google.com/amp/s/www.forbes.com/sites/lorenthompson/2015/09/23/boeing-to-build-its-first-offshore-plane-factory-in-china-as-ex-im-bank-withers/amp/  What you're talking about with computer tech still being stronger in the US vs China is a common misconception. Though we are a powerhouse worldwide in CS with people all over the world using sites like Facebook and google, China made a smart decision years ago to block these sites and have their own similar sites developed in country. These sites are every bit as powerful and almost as commonly used as their American counterparts.   As far as the language and cultural barriers go this is a barrier that the Chinese are easily and quickly overcoming (just as Korea and Japan had done in the past). China is the biggest international market for consuming American made entertainment and Americans and Europeans are moving in the thousands to China to teach English and teach western customs.(my sister has been teaching English there for the last 3 years)  Finally, the Trump bullshit. I guess you could say you're guess about his lasting effects on our country are as good as mine, but I think we could both agree that they wont be good. Note that the pros pay for extremely fast access and are literally fighting over nanoseconds to get every possible advantage. Your system won't come close to that by several orders of magnitude. Consider the implications for the kinds of automated trading you want to perform. (Pico was overstating it. Nano, at the processor level and in terms of which transaction is first into the buffers, is certainly true. A millisecond is a Long Time in this domain.) "A lot of people have already explained that your assumptions are the issue, but I'll throw in my 2¢. There are a lot of people who do the opposite of long term investing.  It's called high frequency trading.  I'd recommend reading the Wikipedia article for more info, but very basically, high frequency traders use programs to determine which stocks to buy and which ones to sell. An example program might be ""buy if the stock is increasing and sell if I've held it more than 1 second.""" CFDs should not be used as a buy and hold strategy (which is risky enough doing with shares directly). However, with proper money and risk management and the proper use of stop losses, a medium term strategy is very plausible.  I was using CFDs in the past over a short time period of usually between a couple of days to a couple is weeks, trying to catch small swings with very tight stops. I kept getting wipsawed due to my stops being too tight so had too many small loses for my few bigger wins. And yes I lost some money, almost $5k in one year. I have recently started a more medium term strategy with wider stops trying to catch trending stocks. I have only recently started this strategy and so far have 2 loses and 3 wins. Just remember that you do get charged a financing fee for holding long position overnight, buy for short position you actually get paid the funding fee for overnight positions. My broker charges the official interest rate + 2.5% for long positions and pays the official rate - 2.5% for short positions. So yes CFDs can be used for the longer term as long as you are implementing proper money and risk management and use stop losses. Just be aware of the implications of using margin and all the costs involved. If the car is in otherwise good shape, it's always less expensive to keep it longer. Think of it this way: you have to buy new tires no matter what. It's just a question of whether or not those new tires are attached to a new car or your current car.