You can only surmise that there are 5K "difficult" cases that are taking much longer to approve than the normal processing time....
difficult cases theory is good. But that doesn't explain why we don't see 1000s cases for recent months. On the other hand yes there are difficult cases but they are from years behind. As far as 2009 or 2010 goes they are all legitimate cases of recently approved PERMs that came into inventory recently. Lower 2010 cases suggest that low number of PERM are approved for 2010 for ROW EB2. So it is safe to take 500 (which is the max number) in inventory and extrapolate to get total annual demand. What I missed was although annulized demand is 5K, in 2010 multiple years of annual demand hit. They already had 2007. But then they received 2008-full/09-full/10-partial. However even if we asssume it was 5-8K per year.. that gives us 15-24 max. Then take out 9K that is today that still says that EB2ROW only ate 6-15K max in 2010.
.....
But let's do that and use the average pending amounts over the 5 Inventory Reports published so far.
Average Pending EB2-ROW = 6,118
Average Pending EB2-Mexico = 190
Average Pending EB2-Philippines = 523
Average Pending EB2 (excluding China & India) = 6,831
Since that is for 3 months, multiply by 4 for yearly total = 27,324
This is difficult to agree to because difficult demand stays there for all 12 months. whereas only the flow-through demand should be qualified for annualization. Right?
Whilst I have my doubts about using this approach, it does at least give a result that we know is in the ball park of historical accuracy.
If USCIS decide to have a clear out of cases just prior to the Inventory publication, then all and any bets are off since it distorts the figures.
Looking at EB1 Worldwide in the same way gives a demand of 15,287 for the year.
I don't believe that figure in the light of all other evidence to the contrary and, whilst the EB2-ROW-M-P figure might look reasonable, it therefore can't be trusted either.
So, I will reiterate my view (probably annoyingly

)
Don't worry at all. This is all good discussion!