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发表于 2004-9-4 19:49
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Money Management 8
Money Management
An essential element to success in trading is ignored in almost all trading or market timing books or articles. It's surprising given its importance that very few writers devote any time to the discussion of money management practices and principles. This chapter will present one approach to money management that is general and could be easily supplemented by other methods if you desire. The goal here is to provide recommendations for a simple, viable approach to allocating funds and managing your portfolio.
This book is not intended to include a course on money management. However, if there is one subject within the realm of trading that is vital to a trader's financial survival and at the same time totally overlooked as critical, it is the discipline of money management as it applies to trading success. If market indicators and systems were always precise in identifying tops and bottoms, the necessity for prudent money management skills would not exist.
Unfortunately, such is not the case. Even if a system were 99 percent accurate, the 1 percent failure rate could conceivably wipe out a trader who did not apply money management methodology. The following techniques for your consideration in designing a prudent and viable money management program may appear simplistic upon first glance. However, making procedures complex serves only to obfuscate the obvious, easy, and straightforward approach to sound money management. These recommendations regarding the design of a money management methodology are a compilation of various techniques I have developed and employed successfully throughout the years.
Before you enter any trade, you should be convinced that the trading event will prove to be profitable. Otherwise, why even attempt the trade? Obviously, no decision in life is always correct and this applies invariably to the markets. In the case of the markets, however, you are not able to undo a bad decision and recover your losses from a trade.
This lesson came early in my career. Discretionary decisions or trading hunches or guesses may prove profitable on occasion, but how do you quantify and duplicate this decisionmaking process in the future? Consequently, the following suggestions are directed not only toward developing -a series of mechanical, objective approaches to trading decisions and money management but also to enable you to replicate your decision-making process regardless of the time period and the number of markets followed. The primary considerations are consistency, objectivity, and portability. Additionally, you need to be sensitive to diversification of market timing techniques, as well as markets monitored. By implementing a number of unrelated methods, you will be able to sufficiently diversify your portfolio and thereby reduce your level of risk. In other words, by applying a combination of market timing approaches, each of which uses a different trading philosophy, you will be able to operate as if you had a number of trading advisors managing your funds. Obviously, these techniques should be applied on paper before introducing them real time into your trading regimen. Once the techniques have been sufficiently tested to ensure performance results and nuances, the money management disciplines must be introduced. The other chapters of the book pertain to the methodologies, so this discussion is devoted to a basic approach of managing trades and your investment.
First, you should allocate percentages of capital equally to various mechanical market timing models. Therefore, if you have developed and decided to use three noncorrelated mechanical approaches, then you should designate the same percentage participation to each. You may choose to vary this approach. For example, if one system is two times more effective than another, then you would double by position size or if the frequency of trading for one method is twice as active as another technique, you may wish to reduce portfolio commitment by 50 percent.
However, for sake of discussion, assume that all systems are equally effective. Assuming a total of 100 percent, you may not wish to allocate in total more than 30 percent to these systems collectively at any one time. Also assume for purposes of simplicity that you have elected to follow 10 individual markets for each system. Consequently, your maximum exposure would be no greater than 30 percent of your beginning equity, and that is only if each model has its maximum investment exposure of 10 markets at any one time and each market is being traded simultaneously at the same time (10 markets times 3 trading methods times 1 percent apiece equals 30 percent exposure).
How are you to measure your investment commitment in terms of number of futures contracts, for example? Rather than subscribe to an esoteric portfolio management methodology with numerous complicated variables connected by advanced statistical formulas, you should rely on the market itself to dictate your level of exposure at any point of time. Specifically, the various futures exchanges determine the margin requirements to trade markets. Typically, as trading activity becomes volatile, the margin requirements increase. At that time, you should reduce your exposure because you would have specifically allocated only a 1 percent commitment to that market for this particular market timing method. Conversely, when price activity becomes inactive and less volatile, you would increase your investment exposure, hopefully, awaiting a breakout and increased volatility. Consequently, margin requirements serve as a barometer for fund allocation.
To clarify this process, the market itself is the best source for dictating market exposure. This measure can easily be determined through simple calculations. The various futures exchanges evaluate the volatility and volume of markets continuously. If for any reason, they believe that the potential exists for wide daily swings in the market and, concurrently, the risk of erosion of a trader's margin, then, typically, they will be inclined to raise margin requirements. Therefore, whenever margin requirements are raised, market exposure as measured by the number of contracts traded should be adjusted accordingly. In other words, say you assume a portfolio size of $1 million, the use of three trading systems, and the limitation of trading only 10 markets in each. The maximum exposure can be no greater than $300,000 dollars, since that amount accounts for 30 percent of $1 million, the maximum account size defined above. It is unrealistic to assume that positions will exist in each and every market at any one period of time, however. In any case, this allocates $100,000 to each of three markets. In turn, this would imply that for each method, each market would represent $10,000 dollars. Now suppose the margin requirement in one market is $ 1,000. Then 10 contracts could be traded at any one time. If volatility increases, the exchange may decide to raise margin requirements by an additional $1,000 to $2,000, thereby forcing you to reduce your position size to five contracts (5 x 2,000 = $10,000 and 10 x $1,000 = $10,000). What has effectively occurred is a portfolio contract-size adjustment of 50 percent due to a 100 percent increase in margin requirements. If the volatility has increased sufficiently that the exchange is compelled to raise margin requirements, and you are still positioned in the market and have not been stopped out of the trade, then it is likely that the market has moved in your favor. In that case, the money management discipline and methodology described here requires closing out profitable positions, and prudent trading would also dictate profit taking. The initial exposure was a function of margin requirements, and the change was made as a result of market volatility and potential risk as defined by the increase in margin requirements.
Once in a trade, stop losses must be introduced. Generally, you should apply a standard stop loss and not risk any more than 1 percent of your portfolio on any one trade. Should you desire to increase this stop loss, you should reduce accordingly the size of the position or exposure you have in that market and at that method at that particular time.
For example, you should always maintain a 1 percent risk level, but if you wanted to increase the dollar stop loss to double that amount, you should reduce your market exposure by 50 percent. All other increases in stops would be adjusted accordingly as well.
As the portfolio size in one method and in one market increases, you should adjust your stop loss and profit-taking levels and make certain that your exposure does not constitute an undue weighting in the portfolio. In fact, as the profit in a position increases, you should reduce the position size to maintain a maximum portfolio exposure and, ideally, in effect you will be investing only the profits generated in the trade.
The approach described here is simplistic but effective. High-tech mathematical modeling and sophisticated statistical techniques can be introduced, but experience indicates that minimal improvements will be produced.
Although this approach to money management is devoted to high-margin futures, a similar approach can be easily applied to stock portfolios.
In conclusion, it is critical that a trader design and implement a methodology that is capable of being measured for performance statistics historically. Once confident of the results and comfortable with the implementation, a trader should paper-trade the method and then apply it real time to the markets with funds in small lots or shares. As you gain experience and confidence with the method, the position size can increase. Discipline is a prerequisite. If you conform to the general money management guidelines discussed in this chapter and then add improvements to the schedule to fill in any blanks in procedure, a difficult and critical component of trading success will have been addressed and satisfied.
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The Kelly formula
A simple case of the Kelly formula is where you either double your wager (i.e. you get back your bet plus an equal amount) with probability p or else lose it all with probability q = 1-p . The Kelly system says that in this case the optimum fraction of your capital to risk is f=p-q.
For example, if you have a system in which you double your money with a 60% probability and lose it all with a 40% probability then your optimal fraction to bet is
f = p - q = 60% - 40% = 20%.
The mathematical reason that its true is actually quite simple.
In the double or nothing case above, the log of your return per bet after W wins and L losses using this system is:
(W/N) log(1+f) + (L/N) log(1-f) where N=W+L.
If N is large then W/N=p and L/N=q. Maximizing this expression in f using calculus gives f=p-q, as expected.
Thus, if the assumptions are satisfied, your portfolio will grow at the highest rate if you invest the optimal f each time. One problem with the Kelly criterion is that it implies a larger maximum drawdown than most people would be comfortable with. Most people would likely want to choose a fraction to bet which is less than the Kelly fraction even at the expense of optimality. Another problem is that you often don't know what p is.
For purposes of illustration, I have used the same simple double or nothing setup that Kelly uses in his original article but the entire idea generalizes substantially beyond this.
Since you probably don't know what p and q are you could just pick an X% and Y% that are sufficiently small. For example, you could choose X% as 3% or 5%, say. A number of practically oriented books and articles recommend that sort of approach.
William Gallacher's book, Winner Take All, is another source which mentions and critiques Optimal f in the context of futures trading.
Louis Kates
lkates@alumni.princeton.edu
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Tips & Hints:
Should you desire to increase this stop loss (1% of cap.), you should reduce accordingly the size of the position or exposure you have in that market and at that method at that particular time. ð adjust stop loss and profit-taking levels
As the profit in a position increases, you should reduce the position size to maintain a maximum portfolio exposure and, ideally, in effect you will be investing only the profits generated in the trade (!).
Random Entry Strategy:
The initial strategy demands that with any trade on, right or wrong, the stop and exit system would either leave you in the good trades or get you out of the bad trades at a small loss and under certain circumstances get you on the other side. The random initial entry perspective forces you to develop a very disciplined trading strategy and trading rules to go along with it. More importantly, it gets you away from looking for all the answers in the various entry systems which were being promoted.
The stop and exit rules for the system were developed with an extreme perversion to optimized values and being very careful to watch the degree of freedom which I allowed the system to have. Once you have a set of profitable stop and exit rules, you can concentrate on developing an entry system that was more intuitive than the random 'flip of the coin' method. This step in the development of a system, by definition, became much less important.
The importance of discipline in your trading regime can not be overstated, especially on exits. This discipline was a welcomed (and badly needed) side effect of developing a trading system with this methodology.
Trailing or multiple contracts:
Enter all contracts on the entry and exit half (or a portion) at the primary exit signal, stop is moved to breakeven on the remainder and we trail the remainder until the secondary target or we get stopped out. Each trade has an associated stop plus a primary and secondary exit ð at the time of entry, all possible exits signals are known and quantified
I use threshold levels to increase my trading size. My formula is:
2x max historical drawdown + margin = equity needed to trade 1 S&P contract.
So a 50% drawdown to me means a real 25% drop in equity.
By drawdown I'm talking about my total net running drawdown. I always use stops on my individual trades which keeps my max. daily net loss around 3% to 5% depending how many systems trade that day (I use 3 systems). The recent volatility in the S&P's has forced me to almost double my stops over the last 6 months which has made the drawdowns deeper.
Turtle System trading signal:
1. Enter a long/short when a tradable (!) exceeds its 20 day highest/lowest close.
2. Exit a long/short when a tradable (!) reverses to inside its 10 day highest/lowest close. (wenn letzter "theoretischer Trade" ein Verlust war, nur eine Position eingehen [theoretischer Trade: wenn weitere Kriterien' nicht erfüllt?])
The second part on money management describes when to increase or decrease the number of contracts traded.
The hint I can give is "volatility". Focus on the volatility of each individual market. Then think of in terms of "units". Derive your starting capital into measureable "units" based on volatility.
The Turtles managed the absolute risk this way:
1. Take the average of the True Range over 10 days
2. If this is rising, trade with FEWER contracts. This allows the stop (=risk) to be
wider and so you risk a constant amount of money but with fewer contracts
3. If average TR is lower, then start trading more contracts
Trailing Stop:
Let's say you buy an S&P at 900 and it rises to 902. If the S&P stays above 902 for a week and then falls below 900, say to 898.40 then you get stopped out at that point, 898.40, assuming no slippage. A Trailing $400.00 trailing stop would get you out at 900.40 assuming that the S&P did not get any higher than 902.
Risk-Reward-Ratio:
10% risk per trade: you may think, that if you have 100000 you could risk/invest no more than 10000 in one stock (e.g. 50 stocks á 200). But consider buying a stock priced at 200 with a 2$ stop loss: risking 10% means, one could buy 5000 stocks ! So risk must be thought of as the percent of equity you are willing to lose on a trade if you are wrong. Risking more than 3% is extremly risky, especially if you have 10-15 positions on at one time. |
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