I’m pretty sure I’ve posted this map before. It’s not surprising, as it shows fertility differences across the nation.
But, what I just realized is that the fertility rate gradient between West Bengal and Bihar is one of the largest in the world. Bihar’s TFR is about 3.3, West Bengal’s 1.6. For comparison, Mexico has a TFR of 2.1, and the USA 1.7. Yemen has a TFR of 4.0, and Saudi Arabia 2.5. Perhaps analogous are Iran and Pakistan. TFR’s of 1.7 and 3.5, respectively.