I've forgotten where I read this, though I believe it was FAA material on the FAA website.
I recall seeing a chart with a curve, that showed the accident rates of new pilots based on the number of hours flown. The left vertical axis had a scale of the number of accidents per 100,000 hours. The bottom horizontal axis had a scale of total hours flown by the pilots in the study. The curve went down from the upper left (low hours-high accident rates) towards the lower right (higher hours - lower accident rates), finally reaching a flat line of a low stabilized accident rate (I can't remember that rate now) at around 800 hours. As I remember, the curve was fairly flat from 600 to 800 hours, but was quite steep prior to 600 hours.
What my mind remembers most about the chart, was that a new pilot had to reach the 600 to 800 hour mark, before he/she could consider themselves experienced enough to be truely skilled and safe pilots. Prior to at least 600 hours, a lot of diligence is required on the part of the pilot, to make sure you stay within you'll level of competence to remain safe, while still developing and learning new skills. Even after learning new skills, you still have to gain enough experience using those skills, for them to become automatic and second nature to you.