I Don't Think You Can Predict Approvals.
I do not believe that you can make a blanket prediction about approvals.
My understanding of the process is as follows. There are 2 security checks on your case, one at the beginning and one at the end. This is done via an inter agency checking process. It would seem that BCIS get responses on more than 95% of cases. Under the new security rules they need to get a positive response on your case in order to move forward. If for some reason they don't, they do not seem to have a good process to close these cases out and this explains some of those people with 'old' cases. I think there is also a class of cases where there is a question in the case that does not require an RFE, just a second opnion. I think some of these cases tend to sit around as well. The third class is the unlucky, lost file etc.
These exceptions do not affect the majority of cases, and contray to popular opnion I think there is a pattern to when BCIS will get to a case. It is clear from the script (greenland) data that there is more than one population of of I-485 cases. Family (I-130 cases) get processed in a much shorter timeframe than EB (I-140) cases. On EB cases Rupnet has given us an excellent insight into what NSC is doing at a high level. But only until the case is touched by BCIS.
There was a clear pattern during 2003 for case processing. NSC would start one month, then over the course of 12-16 weeks, process direct approvals and RFE's on all of the cases that did not fall into the holes described above. 2004 has not followed this pattern. 2004 started with minimal work being done on Feb 02 cases, this then seemed to stop and NSC began working on April/May 02 cases. Over the last 4 weeks though they have started working Feb/Mar cases.
So given past performance, my opinion is that there is a 90% - 95% chance that any outstanding case with Feb - May 02 RD's will be touched (direct approval or 1st RFE), within the next 12 weeks.
The problem in actually forecasting approvals is the RFE. RFE's are specific to cases, so you can't make assumptions about how complex the decision will be regarding the evidence. As I have said before the need for a second opinion case can cause a case to go into limbo. The second problem is that you get 87 days to respond to an RFE, so you have a number of other things to consider. How long it takes for the RFE to get from the NSC mail room to you or your lawyer. How long it takes the lawyer to look at the RFE and pass on the request for information to you. How long it takes you to gather it. How long it takes the lawyer to put that in a package back to BCIS. All these things add an unpredictable amount of time into the process.
Looking at Mar 2002 cases. There are 18 approved cases in Rupnet with an RFE. The time between RFE and approval ranges from 21 to 217 days. The average is 51 days. If we remove the two highest and lowest values, then the average is 40 days. Is this predictive, I don't know. If you look at earlier RD months then the RFE/Approval processing period can stretch to around a year.
In any case I have attached my latest analysis to this.