USCIS recently updated the I-485 pending inventory. The only problem is the data is as of April 2, 2013 (nearly 50 days old).
You can view the April 2, 2013 inventory here: http://www.uscis.gov/USCIS/Green%20Card/Green%20Card%20Through%20a%20Job/I-485%20Employment-Based%20Inventory%20Statistics/EB%20I-485%20Pending%20Inventory%20as%20of%2004-02-2013%20Final.pdf
We were hoping the data would be current so that it would include thousands of new cases filed in EB3 ROW categories since May 1; but it looks like we may have to wait for another three months to get that data.
This new data would definitely help in updating the GC calculator tool; though it might take few additional days to do in depth analysis.
Q. What is not included in I-485 pending inventory
A. I-485 pending inventory does not include (a) consular processing cases which is around 15% of total 140,000 visas allotted each year (b) if I-140 is approved but I-485 application is not filed, then it will also not appear in this inventory (c) I-485 applications which has already been approved.
If I-140 and I-485 is concurrently filed, then the applicant will not show up in inventory unless I-140 is approved.
Please see this article for more details: FAQ: I-485 Pending Inventory.
You can see all the previous I-485 pending inventory here: