Does it still make sense if I omit "of the time" here?
No, it would not make sense if you omitted "of the time" here. This is because "50 percent" indicates a fraction of something else, so if you just said "50 percent" it would not make sense. Therefore, you must keep "of the time" here since the "50 percent" is referring to half of the total amount of time.
Get more Native English Expressions >