In 1973, 580,000 mobile homes (or manufactured home as they are now called) shipped in the United States. This represented about 50% of the number of single-family housing starts that year, and about 22% of total housing starts. So they represented a significant chunk of the overall housing supply.

But following the collapse of the US housing market in 1974, an interesting thing happened. Manufactured homes never managed to reclaim their position in the stack. See above chart. Brian Potter, author of Construction Physics, puts forward a number of possible explanations for this, over here.

Some have speculated that it was the result of new code changes that ended up increasing costs. Some have speculated that it was because of a new requirement to include a steel chassis on the bottom of every home, which also increased costs, but more importantly stigmatized manufactured homes. It made them seem transient, whereas previously they were installed on permanent foundations.

There are also some theories that manufactured home production was harder hit during the economic downturn given that they had more fixed plant costs (compared to site-built homes with their variable labor costs).

But Brian's current working theory is that it comes down to capital flows. Manufactured homes tend to cater to lower-income buyers and so supply, as the argument goes, has largely depended on "lax lending" practices being made available to them.

I'm not so sure that this is the only reason though. For one thing, multi-family housing starts have followed a somewhat similar trajectory to manufactured homes. We've certainly seen an increase in supply over the last decade, but we've never gotten back to that early 1970's peak.

And so I wonder: How much of this is actually just the result of the single-family home hegemony? This is arguably what the market has historically wanted (look at the split pre-1973 in the above chart), and so perhaps we simply refocused our attention there and worked to make this housing type as accessible as possible to the masses.

Chart via Brian Potter