Take a look at the accompanying chart from this NY Times article (may require subscription if you have used up your monthly 20-article viewing allocation). It gives you a sense of the different types of early applications that exist as well as the acceptance rates. Note that many schools offer both binding and non-binding Early Decision and Action options and some schools do two rounds of Early admissions.
The article mentions that those who opt for early admissions usually have well-informed and sophisticated college advisors, who can assess a student's chances effectively based on the school of choice. Therefore the admitted rates can be misleading - it is not the average student that applies for a particular school, but relatively above-average candidates; so applicants should weigh that as a factor when deciding.
