IMAGINE YOURSELF WALKING across a field when you suddenly find a deep ditch crossing your path, let us say one of about five feet in width. You now have a choice. Your gradualist approach towards crossing that field - ambling along - has served perfectly well so far and will serve once again when you get to the other side of that ditch - but it will not serve you in getting across the ditch. Keep walking as you were before and you will fall in. The only way to cross the ditch is to step back a few paces, make a brief run and jump across it. There are times in matters of economic reform when the same is true, when gradualist reform can only take you so far before you have a big jump to make. Either the market that you have toyed with opening is opened or it is kept closed. There are no intermediate stages left. The Soviet Union, for instance, faced that choice in 1991. Soviet president Mikhail Gorbachev introduced gradualist reforms that then began to snowball of their own accord into greater reforms and, suddenly, the big decision could no longer be avoided: crawl back the way the nation had come or jump forward. The people jumped, the Soviet Union expired and a market economy was born. It took a leap to go into communism. It took a leap to come back out. The mainland, following in the footsteps of the Soviet Union, made that first sort of leap in 1949, when it adopted a command economy. It is now also turning around to face the leap again on a return to a market economy and, just as before, there will be no easy way across the big divide. When the gradualist approach has taken you as far as it can, you jump or fall. Where that jump is most likely to be made in the mainland is over the big divide of the capital account. If an eventual full opening of the capital account is to mean that the man on the street in Chengdu can freely direct his bank to convert his yuan savings into US dollars and buy shares of Motorola with it, then the days of central control over the mainland economy are over. The money can go where it wants and will no longer be dictated to. What is more, as gradualist reforms take the mainland economy closer to that day, the pace of reform will inexorably quicken, just as it did in the Soviet Union, and Beijing will find its control over the reform process ever more diminished. The run-up to jumping across the ditch will have begun. To stop it then would be to guarantee a fall into the mud. Thus Premier Wen Jiabao is toying with a distinct threat to central control when he says, as he did on Monday after the close of the National People's Congress, 'we are working on a plan to reform the exchange rate system. Regarding the timing of the reform and the specific measures to be adopted, this could possibly be something unexpected.' The statement was followed with the usual talk of carefully, carefully, carefully but there is not likely to be much careful in the way that currency speculators will treat it. This is a red rag to their bull. When a senior politician hints at the end of a regime of rigged exchange rates, they will come streaming in to take advantage. They already have cracks in the wall of that closed capital account to operate through, cracks given them by the first gradualist reform measures, and the immediate result will be another big boost to liquidity in the mainland as they all bet on a revaluation of the yuan. This will place renewed inflationary pressures on the authorities in Beijing and redouble the impetus for an early revaluation. It will do no good for Mr Wen then to say that he had nothing immediate in mind. Currency speculators can wait. Some waited for years ahead of the Asian financial crisis in 1997. If things can only go one way but are delayed in going there, it will only give those speculators more time to build up bigger positions and add further to the pressure. The run will be on its way or, to choose a different metaphor, the proverbial snowball will have started to roll. It will, of course, take much longer for Mr Wen's limited currency reforms to translate into eventual freedom of investment choice for the man on the street in Chengdu but the point about rolling snowballs is that the further they go, the faster they go, the bigger they become and the more difficult they become to stop until they cannot be stopped at all. Methinks Mr Wen may not be fully aware of what he has started here. Just as with Mr Gorbachev in the Soviet Union, he may eventually find to his dismay that it is he who is being rolled over.