The 2000 was the first year that the GPS (Global Positioning System) equipment was utilized to record the location of the fossils.
The 2001 season was the first year that pre-printed numbered Field Labels were used with a more precise control of the field numbers used. The number on the Field Label becomes the permanent identification number for the specimen. The Field Labels are allocated in packs of 100 to the various quarries during the course of the excavation season and a careful record made of numbers assigned to track the fossils in the quarry, as they are removed from the quarry, as they are packed for transport, as they are prepared, and ultimately curated in the collection.
Typically a few issued Field Labels are unused, but several additional numbers are utilized in the course of the bone restoration as small items are discovered as the larger bones are removed from the field jackets.
Quarries with 1 or 2 bones are years the quarry was not worked, but a speciman or two were recovered after being exposed by erosion.
averages do not include years prior to 2001 and years with 2 or less bones
The total number of specimens recovered is not necessarily the best measure of the success of an excavation season. Large or fragile or rare bones typically take much longer to excavate carefully than small bones, teeth, tendons, and bone fragments.
Also the lower threshold for size of tendons and bone fragments to be recorded and recovered has tended to increase as the research has progressed from year to year which reduces the actual counts of cataloged specimens.
A better measure might be the total weight of specimens recovered, but this information is not determined or recorded.