EB2 and EB3 visa number spillover

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Hi friends, 

I was studying the EB2 and EB3 visa number spillover rules and had the following question. 

I found the following statistics:

EB3 FY 2017 Numbers:

• Total Available EB3 = 40,040
• Total Available with Spill Over from EB2 = 40,040 + 0 = 40,040
• Total Issued for EB3 India = 6,608
• Total Issued for EB3 China = 2,348
• Total Issued for EB3 South Korea = 3,290
• Total Issued for EB3 Philippines = 6,492
• Total Issued for EB3 Overall = 34,938

I know that there is a 2800-per-country cap and that unused EB3 visa numbers would be allocated to retrogressed countries. 

But why did China only get 2,348 visas while South Korea and Philippines were getting 3,290 and 6,492. China is more retrogressed than South Korea (South Korea is not even retrogressed) and Philippines. 

 

Thanks!