The average household size declined throughout the 20th century (see graph, below) but the 2011 Census surprised many when it showed that the average size had barely changed over the previous 10 years. The number of one person households had been expected to continue its exponential rise and make up 35 per cent of households by 2011. Instead, one person households only maintained their share of the total.

So what caused our households to shrink? Increased availability of housing during the 20th century, changing lifestyles, increased affluence and support from the state have all enabled growing numbers of people to live in smaller household sizes.

People delaying having children, more women entering the workforce, higher rates of divorce and longer life expectancy, together with NHS and social care, have all played a role in the growing number and proportion of one and two person households.   

The number of two person households has consistently made up around one third of the total for the last 30 years. Meanwhile, the growth in one person households has followed more of an exponential trend by total numbers, though this came to a halt between 2001 and 2011 when their total share of households was simply maintained.

This raises the question whether we have reached a peak in one person households due to people's preferences (peak loneliness), or whether it is the result of constraints imposed by an unaffordable housing market?

Simple trend analysis suggests a combination of these factors contributed to lower proportions of one-person households than expected. Both reaching an optimum proportion of older one person households and an increasingly unaffordable housing market, limiting the ability of younger people to live alone, has tapered the trend. 

Yet the largest decline in the proportion of one-person households is in London (see map, below), the most unaffordable housing market in the country, suggesting affordability pressures are the leading factor. If housing affordability were to ease, then further larger increases in the number and proportion of one person households could be expected.  

Looking forward, it is essential for us to gain a greater understanding of the motivations for why one-person households form and what has been preventing them from doing so.

This will facilitate more accurate forecasts for housing need and ensure we are building the right mix of homes in the right locations. 

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