It works best when comparing people with relatively similar consumption, e.g. asking about the material lives of engineers in east- vs. west-germany. Both had cars, radios, apartments with indoor plumbing, and awful haircuts, but they paid for them with different money. Any exchange rate was basically a fiction, but even if the currencies had been freely traded, these two still couldn't buy each other's goods.
Some people in India have lives similarly comparable to the west, e.g. the class who buy iphones. But the ones who make this super-cheap data interesting really don't. I mean there are riots when the price of onions doubles after a poor harvest. It's difficult to imagine a shared basket of goods which meaningfully captures the comparison here --- between prices experienced by those whose weekly budget can flattened by onions, and people in the US.
Probably a better comparison would simply be to quote daily wages alongside such prices. GDP is about US$5/day, compared to about $175/day in the US.
It's fine to take another normalisation metric - no metric is perfect. The point was that there is a normalisation needed. Far too often I see a comment which states, "Oh! It is just 1$ so cheap!". I chose PPP because it is meant for making parities. So, 9cents may or may not be cheap. We don't know until we use a normalisation factor.
People talk about dog-years too, but past some very crude level there's no avoiding knowing something about about the lives of dogs, or parrots, or goldfish. At which point it's less confusing to use ordinary earth-years for everyone.
It works best when comparing people with relatively similar consumption, e.g. asking about the material lives of engineers in east- vs. west-germany. Both had cars, radios, apartments with indoor plumbing, and awful haircuts, but they paid for them with different money. Any exchange rate was basically a fiction, but even if the currencies had been freely traded, these two still couldn't buy each other's goods.
Some people in India have lives similarly comparable to the west, e.g. the class who buy iphones. But the ones who make this super-cheap data interesting really don't. I mean there are riots when the price of onions doubles after a poor harvest. It's difficult to imagine a shared basket of goods which meaningfully captures the comparison here --- between prices experienced by those whose weekly budget can flattened by onions, and people in the US.
Probably a better comparison would simply be to quote daily wages alongside such prices. GDP is about US$5/day, compared to about $175/day in the US.