At first, entries gradually decreased due to prevailing economic hardships. Fields that were once 75 became fields of 40 as recent as 20 years ago -- and the number was closer to 30 cars on smaller tracks. At that point, fields were tailored to individual tracks and lacked a consistent method.
Those numbers ticked upward to 42 and 36, respectively, until NASCAR -- which had long discussed the need to standardize fields -- implemented a mandatory 43-car field for all three national circuits for the 1998 season and beyond. The first 36 spots are decided in time trials, while spots 37-42 are determined with four provisionals.
The 43rd position is reserved for a former Sprint Cup champion that has not otherwise qualified.