I tried to find average distance between stars in the universe, but came to some different numbers, but either way distance is more than 1 light year. At the same time even largest stars in the universe which have 1400 sun radius are 0.00020584 light years in diameter (by my calculations), so it makes absolutely no sense that 0.5% of universe consists of stars, number should be many times smaller. What I am missing here?
The Wikipedia diagram is giving the breakdown by mass not by volume. Baryonic/leptonic (i.e. non-dark) matter is only about 5% of all matter and of that four fifths of it is in the form of free hydrogen and helium. Of the remaining 1% about half is neutrinos or heavy elements. That means only 0.5% of the mass/energy in the universe is in stars.