How should I compare the population of the countries, in this case Russia and the UK? Like this?
Britain is much smaller in sizes than Russia, however, its population is only in two times less.
The word "sizes" makes me embarrassed, and I'm not sure about "in two times less". What are better ways of expressing the same idea?
In my humble opinion, it's an awkward comparison. What does it mean to be "two times less"?
If I say that X is twice as long as Y, and that Y is 10 feet, I pretty clearly mean that X is 2 times 10 feet, or 20 feet. But if I say that X is twice as short as Y, and Y is 10 feet, how long is X? Does "twice as short" mean "half as long"? Or what? "Twice" means that you are multiplying something by two. But how do you multiply "smallness"?
I think it makes a lot more sense to say "half as big" rather than "twice as small". Or whatever ration you intend.
