The ratio is meaningless, though. If the US population increased by 0.001% and the pedestrian fatality rate went up 9%, the fatalities would have increased 9000x times faster than US population growth.
The per capita or per 100,000 rise would be meaningful. You don't get the per capita rise by dividing the rise in fatalities by the rise in population growth.
I agree the numbers used in the article are not the most explicit, though.