I don't think any house I've ever lived in in my entire life had been built by 1939, with the possible exception of the one in Gasville Terrace, Harrogate, where I lived from the age of 1 to 4 and which might have been constructed between the wars.
So, the backstory to this is that the 1931 Census was completely destroyed in a fire and there was no 1941 Census taken because of the war, so for genealogists there's no universal survey of the nation's population covering the years between 1921 and 1951. That's unless you count the September 1939 Register, taken shortly after the outbreak of World War 2. Conveniently, it's not covered by the law that says you have to wait 100 years before Census returns can be made public, so it's being made available now.
The postcard seems to have been computer-generated from the data specific to each town. Here are the startling facts it proudly tells us about Colchester, on the other side of the postcard:
Mainly labourers and housewives, who'd have thought?
What the postcard doesn't say is that to access the information about a household you have to fork out £6.95 per household, or £24.95 for a bundle of 5 households, or (if you're a Findmypast subscriber, as I am) £18.71 for your first bundle of 5 households then the same as everyone else.
I think maybe I'll wait until the content locusts have descended and fed on the data, then the price will come down and maybe be included in the subscription. Unfortunately, the entries don't include names of parents (which would most interest me), but given that modern Census questions don't include that and there's no need for such information in a quick survey done to see how many people you can conscript into the army, I can't really complain. That said, apparently it gives the dates of birth of the people surveyed, and although some of my ancestors routinely lie about their age, it seems unlikely they'd lie about the month and day of their birthday; that might be enough for me to pin some of them down.
Hmm, I wish I hadn't written this now, I'm actually tempted...