THE Tokyo Sky Tree, a broadcasting and observation tower that will officially open on May 22nd, is 634 metres high (2,080 feet), making it the tallest building in Asia. Is this Japan's last bid to stay on top? For years, Japan was Asia's richest and most powerful economy. It was the first Asian economy to industrialise, and the emerging Asian tigers—Hong Kong, Singapore, South Korea, Taiwan and later China—merely followed in its tracks. Now, however, Japan is steadily being overtaken.

China's economy is now bigger than Japan's, but less noticed is the fact that Asia's so-called newly industrialised economies (NIEs) are, one by one, becoming richer than Japan. Most economists reckon that the best way to compare living standards is to take GDP per person measured at purchasing-power parity (PPP), which adjusts for differences in the cost of living in each country. On this gauge, Japan was overtaken by Singapore in 1993, by Hong Kong in 1997 and by Taiwan in 2010. But the most humbling re-ranking will be when South Korea becomes richer than Japan. The latest forecasts from the IMF suggest that this could happen within five years (see chart). That would be a remarkable turnabout. In 1980 South Korea's GDP per person was barely a quarter the level of Japan's.

Calculated at market exchange rates, Japan's per-head income is still higher than all the NIEs except Singapore. Yet Japan's high prices, especially for housing and food, bring down the country's true standard of living. PPPs are tricky to calculate and economists come up with different numbers, so the IMF's figures are contentious. Some other yardsticks, such as car-ownership rates, still suggest that Japan has a comfortable lead over South Korea. But the trend is clear: the tigers are outpacing their teacher.