Same in Germany (well, lamb (regulated as max age 1 year), I haven’t actually seen mutton anywhere. Even the middle eastern butcher only sells lamb), though we mostly tend to import it from NZ for some reason.
NZ has insane economies of scale and other efficiencies that mean it makes the cheapest lamb in the world. NZ lamb is usually cheaper than Welsh even in UK supermarkets.
Interesting, thanks.
NZ population: ~5 million people, ~25 million sheep
The article specifically talks about lamb being commonly available while mutton is not.