> elderly subset of 5% of the population He's writing a book for a US audience. The US audience uses US customary units for measurement and has done so since '

> elderly subset of 5% of the population He's writing a book for a US audience. The US audience uses US customary units for measurement and has done so since 'forever' basically. The subset of US citizens that knows metric well enough to be comfortable using it for things like cooking is small enough to be irrelevant for his book. Would it be better to use the metric system for everything in the US? Of course. Will it happen in the next 100 years? Nope. And I'm really confused about the elderly part of your statement. Do you correlate being young in the US with knowing the metric system? If so you are unfortunately wrong. Actually you are more likely to find metric knowledge in the general populous in the older crowed due to an attempt in the 70's to convert to the metric system. So, outside of areas that use metric internally, the older population is more likely to know metric than the younger ones.