In our Green Card Tracker we add the number of pending consular processing cases (estimated), to the number of pending I-485 applications (published by USCIS), in order to calculate the total number of people waiting ahead of you. Here we will explain how we calculate the ratio of CP to I-485, which is not published anywhere but can be derived from government data.
USCIS releases pending I-485 inventory on a quarterly basis, so roughly four times a year. The Department of State also publishes the pending Consular Processing inventory, but only once a year. So the first step is to find the most recent matching pair of publications.
For 2011 the Department of State released their Consular Processing Inventory with data as of 11/1/2011. The I-485 Inventories, on the other hand, were published on 05/03/2012, 01/12/2012, 10/01/2011, 05/27/2011, and so on. We can easily see that the closest match is the one released on 10/01/2011. Although we can apply some extrapolation here, it is probably an overkill given the dynamic nature of the data.
Now that we've settled on the data set, let's take China EB-2 as an example:
From the October 1, 2011 I-485 Inventory, the total number of pending China EB2 applications is 4136.
From the November 1, 2011 Consular Processing Inventory, the total number of pending China EB2 applications is 1053. The PDF contains tons of data. you may have to dig around to find what you need. A summary is posted here.
Calculate the percentage of consular processing cases in the total: 1053 / (1053 + 4136) = 20.3%
The latest I-485 Inventory (May 3, 2012) shows the number of pending I-485 for China EB-2 with a Priority Date of May 28, 2008 is 2364.
Now add CP cases which account for 20.3% of the total, we get the final result of 2966.
The DOS inventory report doesn't list all countries or categories. It doesn't mean there are 0 pending applications, rather they are not on the top countries list for that particular category. In this case the green card tracker uses 15% as the baseline ratio.
In addition, the Rest-of-World (ROW) category is not listed separately in the CP inventory. So the ROW values are always calculated by subtracting numbers for China, India, Mexico and the Philippines from the subtotals.