Researchers have given fresh weight to the complaint of many single women – there aren’t enough men.

Kiwi men in their relationship-forming years have disappeared in their thousands, says social scientist Dr Paul Callister.

The result is that men are increasingly outnumbered.

Since 1991, the census has shown a widening gap between the number of women and men aged between 20 and 49, reversing a long history of men having the numerical advantage.

In 1986 there were 700 more men than women in that age group, but by 1991 women had started pulling ahead.

By 2001, the census counted 53,000 more women than men aged 20-49, or just under 7 per cent more women. About 1.5 million Kiwis are in this age group.

Callister and Professor Richard Bedford of Waikato University are to probe migration and census data in countries such as Australia to find out what has happened to the Kiwi men.