The number of people living alone is expected to increase dramatically over the next quarter-century while the number of family units declines, new figures show.

The latest demographic forecasts published yesterday by the General Registrar for Scotland predict that the number of single households will increase from 809,000 to 1.2 million - or 44% - between 2006 and 2031.

Meanwhile, the proportion of people living in a traditional family unit, two parents with one or more children, is expected to decrease by nearly one-third, from 443,120 to 299,840.

While some changes can be accounted for by Scotland's ageing population, which will see more elderly people living on their own without children, one of the biggest increases in house type is among single men - from 353,000 households in 2006 to 554,000 in 2031.

Although the trend has been known about by demographic experts for decades, the latest figures show that trajectory is steeper than had been thought.

Experts said this had been bolstered by Scotland's strong economy, slowing the exodus of people leaving to find work and persuading others to return home; immigration from eastern Europe; and birth and death rate changes.

The average household size is projected to fall from 2.19 people in 2006 to 1.93 in 2031, according to the estimate. This will have profound and wide-ranging impacts on Scotland's housing market and the social make-up of neighbourhoods.

While the recent credit crunch appears to have impacted most negatively on small, two and three-bedroom apartments and demand is still greater for larger, family homes, this situation is expected to have reversed in 25 years.

Whereas traditional families made up 19% of all households in 2006, this is predicted to drop to 11% by 2031.

Duncan Macniven, the Registrar General for Scotland, said: "Over the past 15 years, Scotland's population has increased by 34,000. However, the number of households has increased at a far greater rate - by over 250,000 - because the average household size is getting smaller."

Mr Macniven explained: "Scotland's population is ageing, with more people in the older age groups and fewer in the younger age groups.

"This has an impact on household structure, as children tend to live in larger households, and older people in smaller ones.

"By 2031, one-adult households are projected to increase by almost half and two adult households will increase by a quarter."

The figures also show that the number of households in different local authority areas are projected to change at varying rates.

Orkney, West Lothian and Edinburgh are all projected to have increases of 35%, while in Inverclyde and East Dunbartonshire the number of households is projected to drop by 3% and 2% respectively.