# percentage for... vs percentage of

I find these two structures in the same book:

the figure/percentage/total, etc. FOR a group or category

Ex: If we compare the percentages FOR skilled and unskilled workers...

But on a different page, it has sentences like this

The chart shows the percentage OF households with more than one car.

The percentage OF students with blue eyes is 25%.

So, what is the difference here? Is it possible to write: "If we compare the percentages OF skilled and unskilled workers"? Please help me, thank you.

It depends entirely on what you want to say.

Percentage of is used to indicate a part of a group:

20% of students have blue eyes.

This means that in the group of all students, 20% have blue eyes.

Percentage for is used to indicate a percentage that relates to a group.

Say that we are looking at how much of their income people spend on housing, and we find that skilled workers spend 20% of their income on housing, whereas unskilled workers spend 40% of their income on housing. Those 20% and 40% say nothing about how many skilled worker there are, or how many unskilled workers.

However, when talking about housing costs we can say:

When looking at the percentages for skilled and unskilled workers, we see that skilled workers only spend half as much on housing.

If I would be talking about percentages of skilled and unskilled workers, I would be talking about how many skilled and unskilled workers there are (in a given population).