THIS year’s national-day parade in Singapore on August 9th was the biggest ever, it celebrated the country’s 50th birthday. As every year, the celebration included an impressive display of the island-state’s military fire-power, including, on this occasion, a flypast by fighter-jets, in a formation spelling “50”. It is a reminder of a facet of Singapore outsiders often ignore: that, in terms of its defence spending per head of population, and as a share of government expenditure, it is one of the world’s most militarised countries. Young men must serve two years in the army; new flats in public housing-estates, where 80% of the population live, have “household shelters” with strengthened walls, floors and ceilings.

This is a legacy of the country’s troubled birth in 1965. It achieved nationhood accidentally, expelled from a federation with one neighbour, Malaysia, at a time when both faced a threat from the other, the populous, sprawling archipelago of Indonesia. The sense of vulnerability felt then has coloured policy ever since, even though regional tensions have eased and Singapore is on excellent terms with both neighbours.

Singapore’s leaders credit this paranoia with a big role in the country’s phenomenal success since. Conscious of its fragility, of its lack of any natural resources, of the heterogeneity of its people, and their lack of a shared history, they have worked hard both to make the country an indispensable regional business hub, and to forge a distinct national identity. They have succeeded far beyond the bounds of what seemed possible in 1965. Singapore is now one of the world’s richest countries and has some of the highest “human-development indicators”.

But it still faces two constraints that were obvious at its birth: land and people. By filling in the sea, Singapore has grown by a fifth since then in land area, but it does not have much further to go without bumping into the neighbours. This is a problem since the population has been growing fast and the city’s infrastructure has strained to keep up.

It is also politically controversial that much of the population growth has come from immigration. Despite three decades of encouragement by their government to procreate, Singaporeans are having very few children. The “total fertility rate” (the number of children a woman, on average, may be expected to bear) is especially low among the Chinese majority. Since the government wishes to maintain the ethnic balance (roughly 76% Chinese, 15% Malay and 7% Indian) many immigrants have come from China.