The phrase 'make up a small fraction' is grammatically correct and can be used in written English.
Example sentence: Only a tiny number of applicants have received the scholarship this year, but they make up a small fraction of the total number of applicants.
Temporary employees still make up a small fraction of total employees, but that segment has been rising steeply over the past year.
Although armed drones and airstrikes are most associated with the UAV debate - drones with the capacity to make armed strikes still make up a small fraction of overall trade - just 11 (2.5%) of the 439.
Women represent considerably less than half of the faculty in all but one of Harvard's schools, and while the number of women in tenure-track positions grew slightly from the last academic year to the current one, women still make up a small fraction of the university's tenured professors.
These genes so far make up a small fraction of all human genes.
So far, foreigners make up a small fraction of the visitors to Kerala.
Girls make up a small fraction of the children who play in chess tournaments, and women competitors are even rarer.
Online lending still makes up a small fraction of the $12 trillion in consumer loans outstanding.
In Europe, live donor transplantations already make up a smaller fraction of all kidney transplants done compared with the USA as low as 7% in Bosnia and Herzegovina [ 4– 6].
Acela made up "a small fraction" of Bombardier's railroad business, he said, "but it has high visibility".
Minority students made up a small fraction of total test-takers, making the margin of error for minority scores greater than for scores cited as a national average.
Television is still the primary means by which the campaigns reach voters by the millions, and even now, Internet advertising makes up a small fraction of the candidates' advertising budgets.
