2005 October (Visa number current),
Most people should submmit the I-485, and I know some people get the approved.
2007 July (Visa number current),
Most people should submmit I485.
2008, September (Visa number 2006,August) The missed should get the opportunity to submmit.
So,fewer people have not submmitted I485 as PD is ealier than 2005 October,
also, fewer people have not submitted I485 as PD is ealier than 2006, August.
Thus, The number with I485 PD earlier than 2006 August almost reach the the true data.
Intersting issue is that I canot figure out why some cases can be submitted after July 2007, even few cases in 2008, 2009.