Arbitrage Math

[Minette Mccandrew]

Iam researching about betting arbitrage and I always like to understand why formulas solve for certain things when based on their variables in the equation, don't seem like they would solve for said thing. In this case, I am wondering about a formula for betting arbitrage. I understand how to determine the market-derived implied probability (including a vig) of an outcome with fractional odds or decimal odds and the intuition behind it.

What I cannot understand is the formula of how to determine how much to bet on each outcome to guarantee yourself arbitrage. (given an event where the implied probability of both possible outcomes sums to less than 100%).

This question is somewhat related to my previous question here but has not been addressed in any other thread. The answer in that thread hit the nail right on the head with that one line "Textbooks will go into far too much material if you plan to read them cover to cover, and hence you have little idea of when to stop reading a textbook." I want to get validation on my current approach and if there are loopholes, I'd greatly appreciate any suggestions to cover them up.

I wish to gear up towards a career in hedge funds as an arbitrage quant. I have a PhD in EE majoring in Analog IC design with 12+ years of experience in the industry. I am well versed in linear algebra from my education in engineering. The following is what I think I need to study.

Next, I plan to study Rene Schilling's book on measure theory. As with #1 above, I really doubt if I have to go deeper into books like Billingsley's. Is it really necessary to study Billingsley's book before moving on to the next stage?

The more books that get added to this list, the longer it will take for me to get to the end of it which is perfectly in line with the answer given in the thread I have pointed out in the beginning of this question. So if I am looking at the infima of all the material needed to make an entry into a hedge fund as an arbitrage quant, would that be #1, #2, and #3 mentioned above or is it more than that?

The major gaps in your knowledge, from the point of view of statistical arbitrage, are not mathematical. Most or all of them are not even statistical. Rather, they are gaps in knowledge about arbitrage, and how to take part in it.

PhDs with more than enough skill in measure theory, control theory, SDEs, PDEs etc are a dime-a-dozen. Hiring managers are more concerned about whether a candidate can actually use those skills in a meaningful way -- nobody will assign 1-3 other employees to implement ideas from some rookie math primadonna who does not even know the markets.

In principle and in academic use, an arbitrage is risk-free; in common use, as in statistical arbitrage, it may refer to expected profit, though losses may occur, and in practice, there are always risks in arbitrage, some minor (such as fluctuation of prices decreasing profit margins), some major (such as devaluation of a currency or derivative). In academic use, an arbitrage involves taking advantage of differences in price of a single asset or identical cash-flows; in common use, it is also used to refer to differences between similar assets (relative value or convergence trades), as in merger arbitrage.

If the market prices do not allow for profitable arbitrage, the prices are said to constitute an arbitrage equilibrium, or an arbitrage-free market. An arbitrage equilibrium is a precondition for a general economic equilibrium. The "no arbitrage" assumption is used in quantitative finance to calculate a unique risk neutral price for derivatives.[2]

Arbitrage-free pricing for bonds is the method of valuing a coupon-bearing financial instrument by discounting its future cash flows by multiple discount rates. By doing so, a more accurate price can be obtained than if the price is calculated with a present-value pricing approach. Arbitrage-free pricing is used for bond valuation and to detect arbitrage opportunities for investors.

For the purpose of valuing the price of a bond, its cash flows can each be thought of as packets of incremental cash flows with a large packet upon maturity, being the principal. Since the cash flows are dispersed throughout future periods, they must be discounted back to the present. In the present-value approach, the cash flows are discounted with one discount rate to find the price of the bond. In arbitrage-free pricing, multiple discount rates are used.

The present-value approach assumes that the bond yield will stay the same until maturity. This is a simplified model because interest rates may fluctuate in the future, which in turn affects the yield on the bond. For this reason, the discount rate may differ for each cash flow. Each cash flow can be considered a zero-coupon instrument that pays one payment upon maturity. The discount rates used should be the rates of multiple zero-coupon bonds with maturity dates the same as each cash flow and similar risk as the instrument being valued. By using multiple discount rates, the arbitrage-free price is the sum of the discounted cash flows. Arbitrage-free price refers to the price at which no price arbitrage is possible.

The idea of using multiple discount rates obtained from zero-coupon bonds and discounting a similar bond's cash flow to find its price is derived from the yield curve, which is a curve of the yields of the same bond with different maturities. This curve can be used to view trends in market expectations of how interest rates will move in the future. In arbitrage-free pricing of a bond, a yield curve of similar zero-coupon bonds with different maturities is created. If the curve were to be created with Treasury securities of different maturities, they would be stripped of their coupon payments through bootstrapping. This is to transform the bonds into zero-coupon bonds. The yield of these zero-coupon bonds would then be plotted on a diagram with time on the x-axis and yield on the y-axis.

Since the yield curve displays market expectations on how yields and interest rates may move, the arbitrage-free pricing approach is more realistic than using only one discount rate. Investors can use this approach to value bonds and find price mismatches, resulting in an arbitrage opportunity. If a bond valued with the arbitrage-free pricing approach turns out to be priced higher in the market, an investor could have such an opportunity:

If the outcome from the valuation were the reverse case, the opposite positions would be taken in the bonds. This arbitrage opportunity comes from the assumption that the prices of bonds with the same properties will converge upon maturity. This can be explained through market efficiency, which states that arbitrage opportunities will eventually be discovered and corrected. The prices of the bonds in t1 move closer together to finally become the same at tT.

Arbitrage is not simply the act of buying a product in one market and selling it in another for a higher price at some later time. The transactions must occur simultaneously to avoid exposure to market risk, or the risk that prices may change in one market before both transactions are complete. In practical terms, this is generally possible only with securities and financial products that can be traded electronically, and even then, when each leg of the trade is executed, the prices in the market may have moved. Missing one of the legs of the trade (and subsequently having to trade it soon after at a worse price) is called 'execution risk' or more specifically 'leg risk'.[note 1]

In the simplest example, any good sold in one market should sell for the same price in another. Traders may, for example, find that the price of wheat is lower in agricultural regions than in cities, purchase the good, and transport it to another region to sell at a higher price. This type of price arbitrage is the most common, but this simple example ignores the cost of transport, storage, risk, and other factors. "True" arbitrage requires that there is no market risk involved. Where securities are traded on more than one exchange, arbitrage occurs by simultaneously buying in one and selling on the other.

Arbitrage has the effect of causing prices in different markets to converge. As a result of arbitrage, the currency exchange rates, the price of commodities, and the price of securities in different markets tend to converge. The speed[3] at which they do so is a measure of market efficiency. Arbitrage tends to reduce price discrimination by encouraging people to buy an item where the price is low and resell it where the price is high (as long as the buyers are not prohibited from reselling and the transaction costs of buying, holding, and reselling are small, relative to the difference in prices in the different markets).

Arbitrage moves different currencies toward purchasing power parity. Assume that a car purchased in the United States is cheaper than the same car in Canada. Canadians would buy their cars across the border to exploit the arbitrage condition. At the same time, Americans would buy US cars, transport them across the border, then sell them in Canada. Canadians would have to buy American dollars to buy the cars and Americans would have to sell the Canadian dollars they received in exchange. Both actions would increase demand for US dollars and supply of Canadian dollars. As a result, there would be an appreciation of the US currency. This would make US cars more expensive and Canadian cars less so until their prices were similar. On a larger scale, international arbitrage opportunities in commodities, goods, securities, and currencies tend to change exchange rates until the purchasing power is equal.

In reality, most assets exhibit some difference between countries. These, transaction costs, taxes, and other costs provide an impediment to this kind of arbitrage. Similarly, arbitrage affects the difference in interest rates paid on government bonds issued by the various countries, given the expected depreciation in the currencies relative to each other (see interest rate parity).

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