Dave mentioned in passing that 0+ would be an unusual blood type.

One might think so when just looking at how the alleles work. All you need is one A or one B allele and then the 0+ would be overruled. One might be tempted to believe that it's 25% each of 0, A, B and AB. But that assumes an even distribution of genes.

My blood type is A+, and I grew up being taught it was the most common one. When I moved to Hong Kong I learned that blood type distribution is not universal. Someone told me my blood type was "unusual".

While A+ is not exactly unusual, in China (and I assume HK) near 50% of the population is 0+, while A+ is at around 25%.

It's also not as dominant in Sweden as I was led to believe. 37% of Swedes are A+ while 32% are 0+.

In the UK and US, 0+ is somewhat more common than A+, the reverse of the Swedish distribution.

https://en.wikipedia.org/wiki/Blood_type_distribution_by_country