Betting on politics: How to split your money

Splitting a bet can be a good way to manage your money. Matthew Partridge explains.

I recommend a simple approach to managing your betting money: split it into equally-sized units and put a single unit on each bet. In the case of a bet that involves more than one outcome, I like to split the unit in a way that is weighted towards the odds on offer. For example, if I'm betting on both candidate A at evens (50%) and candidate B at 3/1 (25%) then I'll put two thirds of a unit on A and the rest on B.

Of course, this raises the question of what proportion of your stake you should put into every unit. On the one hand, concentrating your bankroll boosts your returns by allowing you to invest as much money as possible. It also means you won't be tempted to make bets where you don't have an edge.

However, diversification cuts the risk of being wiped out by a run of bad luck. For example, if you make five bets, each with a 25% chance of winning, then the odds of all five being losers are 23.7%. However, the chance of getting no winners from ten bets is only 5.6%.

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A good compromise is to put no more than 5% of your initial bankroll into each unit. Even if each bet has only a 25% chance of paying out, the chance of losing 20 bets in a row is 0.3%. Even in a politically uneventful year, it should be easy to find at least 20 good opportunities every year.

If this sounds too risky, then a simple alternative is to bet 5% of your current bankroll (ie, excluding any unsettled bets) on each new bet. The advantage of this is that no matter how unlucky you are, you will never end up being completely wiped out since the amount you bet will decrease in line with your remaining cash.

Always remember the golden rule: never bet more than you can afford to lose. It is also a sensible idea to keep your bankroll separate from the rest of your money, which will help you resist the temptation to dip into your savings to fund bets.

Dr Matthew Partridge

Matthew graduated from the University of Durham in 2004; he then gained an MSc, followed by a PhD at the London School of Economics.

He has previously written for a wide range of publications, including the Guardian and the Economist, and also helped to run a newsletter on terrorism. He has spent time at Lehman Brothers, Citigroup and the consultancy Lombard Street Research.

Matthew is the author of Superinvestors: Lessons from the greatest investors in history, published by Harriman House, which has been translated into several languages. His second book, Investing Explained: The Accessible Guide to Building an Investment Portfolio, is published by Kogan Page.

As senior writer, he writes the shares and politics & economics pages, as well as weekly Blowing It and Great Frauds in History columns He also writes a fortnightly reviews page and trading tips, as well as regular cover stories and multi-page investment focus features.

Follow Matthew on Twitter: @DrMatthewPartri