Hi Kate,
Thank you for the questions and compliments.
When you say "sell short" do you mean that you're just selling the BTC at that point, or are you actually shorting BTC? I'm not sure if there are many functional sites selling BTC options, though I did see an advert for one claiming to do so called Plus500 (British too!).
At the time of writing, I was shorting through Bitcoinica. These days, I will just exit my entire BTC position and hold cash.
I have always been very skeptical of companies that allow "shorting" in the BTC markets. In the stock market, when you short, someone is lending you a share which you sell and buy back later, while paying interest to the lender. In the Bitcoin market, I have seen no such offering which means that you are engaging in a synthetic short position. A synthetic short means that you are trading against the broker which can be a recipe for unscrupulous behavior.
Also, on your S&P 500 example you refer to "entering a short/long position". Does "entering a short position" in this context basically mean selling the securities (or BTC), and "entering a long position" mean buying back in again?
You are right - in the context of BTC, I consider a short position to be selling coins and holding cash and a long position to be holding coins. In the context of the S&P 500, I call a short position actually shorting the shares rather than just sitting on the sidelines.
To what exactly are you referring when you say "liquidity"? Is is the size of the orderbook in whichever direction you're going (buy/sell)? As an aside, it is a great shame that
CryptoCoin Charts is not yet doing Mt. Gox; they are one of the few sites that provide a visualisation of the orderbook. Assuming I have understood correctly what you mean by liquidity, any tips for those of us not used to looking at a page full of numbers as to how to make that determination quickly?
You're right about this one as well - liquidity is one of those five-dollar finance words that answers the question "can I trade without moving the market?" The best way to gauge liquidity is through the order book. In my opinion, the best one out there is
http://bitcoin.clarkmoody.com/To answer your second question about how to make sense of the numbers: you should already know how much liquidity you need prior to even looking at the book...here's why:
Liquidity protects you from "slippage". Slippage occurs when you place an order at one price and inadequate liquidity causes you to have an average price different from the market price. For example, the current price is $95/BTC. If I were to buy 100,000 BTC, I would "slip" up the book as I ate away the liquidity, resulting in an average price of around $125 per BTC. If I expected to make 10% on the trade but moved the price by 25% when entering, then I have made a mistake by not looking at the order book.
The best way to use the order book is to start with two questions: 1) How many coins will I be trading and 2) What is my expected return on investment. For example, if you are trading the moving average crossover system on an hourly timeframe and expect to earn 3% on each average trade, but you are trading in such a size that you will cause the market price to move 5%, you have inadequate liquidity and need to change your approach.
Finally, I am currently trying BTC/EUR trading on Gox. This is actually because I've a large USD balance I don't wish to risk right by letting BTCbot get at it, but I was also thinking in the longer term it might be a good plan as there will likely be less 10/21 traders on that pair. However, the volume is only about 15% that of USD/BTC (36k vs 6k last time I checked). Do you think the BTC/EUR volumes are adequate for your methods to work / is my idea of switching away from a main pair good?
I have few things to say about this, but I'll cut straight to your question first. This question feeds back into the previous point about liquidity. If you are trading in such a size that liquidity could be a problem in BTC/USD, then you are magnifying your problems by going to BTC/EUR. As liquidity diminishes, your expected return will diminish in that your entry price will be worsened.
Now about BTC/EUR. I don't think I've ever looked at a chart of any other currency vs. BTC, but I'm pretty sure that I know what it shows. Due to triangular arbitrage, all BTC pairs will essentially show the same price movements. For example, if BTC/USD starts rising, but BTC/EUR isn't moving, traders can sell their BTC for USD, convert USD into Euro, buy BTC and lock in a "risk-free" profit. This relationship virtually ensures that as long as money is allowed to freely be exchanged, price movements across currency pairs will be similar. Since the moving average crossover system is a trend-following strategy and the trends will be similar, it doesn't make too much sense to me to change to a less liquid pair.
Best of luck with your trading!