The problem with this sort of analysis is that the average number of people in each household changes over time in response to a range of things, including the cost of housing. Over the 20th century, demographic and social factors, such as a declining birth rate and rising separation rate, were accommodated by growth in the dwelling stock outpacing that of the population.
In other words, there was a downward trend in the number of people in each household (Graph 12). A very similar change was also evident across advanced economies. However, over the past decade or so, these trends have abated and we’ve seen the average household size stabilise.