They were once referred to as the 'empty nesters' – that cohort of the population who, on reaching retirement, were encouraged to sell their family homes and trade down to smaller houses or apartments, freeing up properties that are in high demand.

After a few years of active selling in that sector of the market, it has quietened down significantly, according to figures from estate agents, Savills.

John McCartney, Director of Research with Savills, said it was likely because the nests were no longer empty.

He calculated that of the 51,000 housing transactions carried out last year, about 46% were people moving within the market.

"The official figures don't allow you to look into the composition of that so we looked into our own books. Only about a third of those are downsizing and that has steadily fallen since 2014.

"We're speculating that this is because they have 'boomerang kids' who can't afford to buy or rent and they have no choice to go back home," he said.

The hypothesis is further backed up by preliminary census figures, which show that the number of couples living with children over the age of 20 has gone up by 4% since 2011.

"That doesn't sound dramatic, but when you consider that the number of people in their 20s has fallen by 87,000 between 2011 and 2016, it is quite significant and suggests that they are staying at home longer," he explained.

Official figures also point to the falling number of people over the age of 65 who are living on their own, especially in what might be considered less affluent areas of cities.

Another factor that must be considered in this trend is the perceived lack of suitable properties to trade down to.

"We have an obsession with the traditional family home. Apartment living is still seen as a relatively new concept. The apartment stock is entirely unsuitable. It's not of a quality to entice people out of their family homes," he concluded.

John McCartney also compiled figures on the gain to be made from downsizing.

"The average person trading down is getting a price of €812,000. The average price of buying into the market in a smaller property is €467,000. That leaves a gap of about €350,000 for potential gains for people who trade down.

"The problem is if you sell an expensive asset in a rising market to buy a property that's maybe worth half of that, you're halving the capital gain that you're likely to make."