IN the past fifty years Japan has changed its prime ministers more frequently than most other parliamentary democracies. This has been due partly to the dominance of the rightist Liberal Democrat Party which moved its senior figures around to give each of them a chance of holding the most prestigious post.

Occasionally, however, the Japanese public tires of that game and elects someone who does not conform to the country's machine politics. An example was Junichiro Koizumi, a maverick by Japanese standards, whose long wavy hair and liking for western music, Wagner's and Elvis Presley's especially, made him a popular figure during his premiership a decade ago. He lasted for five years -- an exception who proved the rule. More recently Yukio Hatoyama promised to be different when he was elected eight months ago. He won a landslide victory for his centre-left Democratic Party and undertook to tame the country's dominant bureaucracy, improve welfare benefits and -- fatally -- to persuade the United States to remove its locally unpopular airbase on Okinawa to a more remote location. In this last-mentioned objective he failed totally and has had to apologise publicly. Other shortcomings pushed his poll ratings to 20 per cent from 70 per cent at the time of his election -- a precipitate decline in so short a time. Now the Japanese parliament has to choose its fifth prime minister in four years.