What do you think about as follows:
Only 2% of the country population afford/affords sending their children abroad to study.
On the one hand we should choose "afford" because 2% usually means a great number of people (definitely more than one), but on the other hand 2% can be considered the singular.
What is your view?
I see that my example with "afford" was ill-considered. How about the following:
10% of the country population travel to New Zealand every year
90% of students prefer to take food with them rather than buy it at school