What makes US immigrant visa processing times different? Just select "Petition for Alien relative" I-130 here and you will see a variety of ranges for different categories. What makes them vary?
For Permanent resident filing for a spouse or child under 21, the processing time is 12.5 Months to 16 Months. On the other hand, for a U.S. citizen filing for a brother or sister, it is 108.5 Months to 141 Months.
What creates such difference? Also, does chargeability come into play here, that is does it matter where you were born? Do people from Europe experience less processing times than China or India?