WILL Greece default on its debts and leave the euro? Will Britain decide to leave the European Union? Politicians in the two countries have threatened, implicitly or explicitly, to take these drastic steps if their European colleagues do not offer them inducements to stay.

Many people regard these threats as a bluff. They think that Greece does not really want to leave the euro, and that David Cameron, Britain’s prime minister, does not want his country to exit the EU.

When push comes to shove, Greece will do a deal and Mr Cameron will persuade British voters to stay in the EU in his planned referendum. But there are risks that neither outcome will turn out as planned. In both cases, political leaders are making a risky bet.

The financial analogy is with writing (selling) an option. In the markets, an option is the right to buy (a call) or sell (a put) an asset at a given price; say shares of Apple at $130. In return for granting the buyer of the option this right, the writer receives a payment called a premium, rather like an insurance company receives a premium for protecting a homeowner against fire or theft. But if Apple shares do rise above $130, the buyer of a call option is likely to exercise it, to the writer’s cost; if they fall below it, the holder of a put option is likely to cash in.

Political leaders in Greece and Britain have in effect written an option on exit. The premium they receive is political popularity—for opposing the demands of international creditors, in the case of Greece, or for asserting Britain’s sovereignty, in Mr Cameron’s.

But in the financial markets, option-writing is a very risky strategy, unless the position is properly hedged. A lot of small profits can be earned from the option premia, only for all the gains to be wiped out when an option is exercised at an unfavourable time. Of course, the buyer of an option is most likely to exercise it when the cost to the writer is greatest.

For the political leaders of Greece and Britain, the difficulty is that they do not get to decide whether the option gets exercised. The other nations within the euro zone and the EU may decide to call Greece or Britain’s bluff. In Britain, the electorate also has the right to exercise the option of exit—which they might use in the referendum to protest against government policies in general rather than voting on the merits of EU membership in particular.

This leads to some complex calculations. Unlike Apple’s shares, the price of Grexit or Brexit at any moment is highly uncertain; political leaders cannot be sure what the costs and benefits will be. So this is rather like an option on one of the complex securities that proliferated before 2007—a collateralised debt obligation based on subprime mortgages, for example. The uncertainty makes it less likely that Europe will exercise the option and risk the departure of Britain or Greece.

If that gives the bluffing states an advantage, they also face a difficult trade-off. The more intransigent their demands, the more they may please their electorates (ie, the greater the “option premium”). However, such intransigence may make it more likely that the option will be exercised.

European leaders may feel that making too many concessions to Greece or Britain will simply encourage other countries to make similar demands, and thus destroy the European project. In Britain, there may be a huge gap between the expectations fostered during the negotiating process and the reforms that emerge. This may create the impression that the government has failed, making the public more inclined to vote for exit.

This discrepancy between the high-flying nature of political promises and the mundane reality of policy outcomes lies at the heart of recent voter discontent. Promises may result in short-term electoral success but at the cost of increasing disillusionment in the long term. The most significant short-term influences on growth—the oil price, Federal Reserve policy, China’s success in managing its economic growth—are outside the control of European politicians.

National leaders are, in effect, bluffing when they say their own policies can make much difference.

Europe’s failure to generate much in the way of economic or wage growth over the past decade means that voters are not just turning against the parties in power—they have lost faith with the mainstream opposition as well. The effect can be seen everywhere, from the rise of Marine Le Pen in France to the emergence of brand new parties like the Five Star Movement in Italy and Podemos in Spain. Years of short-term gains for the mainstream parties have resulted in a long-term loss.