For those of you fretting that you won't finish all your college courses within four years, this one's for you — you're not alone. In fact, a majority of U.S. students at public institutions don't finish their four-year degree in, well, four years.

It's what non-profit Complete College America calls the "four-year myth." In a recent report, the organization analyzed graduation and enrollment rates at public universities and found that just one in five full-time students earn their bachelor's degree in four years. At more selective public universities renowned for research, that rate is a bit higher — 36 percent — but still, the majority of students need more than eight semesters to complete their degree program. At community colleges, just 15 percent of students earn their associate's degree or certificate on time.

Across the country, just 50 of 580 public, four-year colleges can say that more than half of their students graduate in four years. So what's holding these grads-to-be up? The report suggested a few factors at the school-level, including trouble registering for required classes, not taking a large enough course-load each semester, an absence of counselors for guidance, and unsuccessful credit transfers from other higher institutions. That last factor may be quite significant since the majority of students transfer to another institution during their college careers.

Now, a little extra time in school wouldn't be so terrible if the cost of higher education wasn't so high. Complete College America estimates that every extra year costs students and families an average of $15,933 for a two-year public college and $22,826 for a four-year.