You have to keep in mind that retrogression is also country specific.
India/China which have many more people going for the greencards then what they are allowed (7.1%) will move slowly.
However, the other worldwide category will not move past april 2001 (the skilled workers who filed in this category are Indian, Pakistani, Nigerian, all over south america, etc.). Until the worldwide category becomes current India will have to wait for years and years, regardless of people buying substitute labors, etc.
As an example:
According to things I've seen was there were over 300,000 labors filed just before april 2001. Approximately 150,000 are going to get approved. Of those 150,000 let's say with dependents (2 on average) that would be 450,000. I think it would be safe to say that India would make up a small portion of this number.
Now in EB3 if there is 28.6% greencards available per year out of 140,000 then there is approximately 40,000 greencards available. If India, China, Phillipines, Mexico take up 7.1% each it would add upto 28% for them and 72% for the rest of the world.
Therefore 2,800 per year for India in eb3 and 28,000 for the rest of the world. If the 28,000 for rest of the world and 450,000 people eligible for April 2001 it would take 15 years for the date to move beyond April 2001.
Now, India could not move beyond April 2001 until the rest of the world moved beyond April 2001.
Let us look at it another way. If no country can get more then 7.1% of the greencards unless other countries don't use up their 7.1% it leaves a few questions open. If every country is eligible to get 7.1%, if you multiplied all the countries in the world, there is no way that this would be possible.
I don't see why they add up the rest of the world together. If each country can get 7.1% of the greencards then small countries, say Luxembourg would not use up their quota, so why would they be retrogressed.
Although it would be difficult they should break down the greencards even further. That is for the rest of the world any country which has less then 7.1% should become current. This has been a mystery to me of why the worldwide category is shown as one category instead of breaking it down even further.