Tuesday, 4 March, 2008

Immigrants and locals

A commentator observed that immigration is a non-issue in Bombay because the fraction of immigrants in Bombay's population has come down from (about) two-third to two-fifth over the last four decades. It didn't sound right. I mean the non-issue bit. So I put in the figures in Solver, and asked it what sort of birth, death, new immigration and immigration from Bombay figures can co-exsist with this drop.

It gave a quite realistic set. People had lots of children. Many new immigrants came. Some of the original locals and immigrants died or moved out of Bombay. Yet the fraction of immigrants went down. How? Simple, I counted the children of immigrants as locals.

While the figures were certainly realistic, they were picked out of the air. So I haven't reproduced them.

But I suppose my point is a valid one. One shouldn't ask people to draw any conclusion from a statistic unless one explains how the figure was reached. Immigration is an issue. To argue otherwise would be dangerous.

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