QSO Counts by Redshift

March 11, 2006  QSO's with published redshift now number nearly 90,000.  This new histogram combines all three distribution surveys.  Peaks still line up fairly closely; the "3.75 peak" is still strong, and the dramatic drop-off in QSO numbers at higher z is still evident.  Notably, at the time of the last survey 2 years ago only 6 objects were found at z 6 or greater.  No further objects in this range have since been identified, despite a doubling of the sample size.

Blue-   2006, ~90,000 objects

Red-    2004, ~48,000 objects

Green- 2002, ~23,000 objects