What are the parameters which will affect exchange rate between two currencies in the long term?

Would like to know how to meanifully forecast exchange rate in between USD and Indian Rupee, both in abosulte terms and in PPT (purchasing power parity), say for next 30 years.

I know this is little difficult question but any theoretical suggestions to calculate this would be useful. India is growing at 8% annually and is expected to continue at that pace. Inflation rate is around 5.5% in India.What are the parameters which will affect exchange rate between two currencies in the long term?The ratio of the median wages for workers in trading industries are an approximation for the exchange rate. Assume wages increase like productivity (GDP per worker) plus inflation. You will also need estimates of the growth of the labor force. Estimating GDP, the size of work force and inflation 30 years in the future has huge uncertainties, therefore so will your answer.What are the parameters which will affect exchange rate between two currencies in the long term?The annual GNP of each nation issuing currency. That's about the best you can do for something like that. Greenspan did something with inflation rate projections but that's a little too far out of my realm.What are the parameters which will affect exchange rate between two currencies in the long term?Interest rates

GNP

Taxes