While both Nifty and Sensex follow the same methodology for calcuation “Free-float Market Capitalization”, the values are different because of following reasons
-constituents Nifty has 50 and Sensex has 30.
-base value - Nifty 1000 and Sensex 100.
-base period - Nifty November 3, 1995 and Sensex - 1978-79
Check the following -
Sensex and Nifty are ever growing indices. [forget about the recession ]
Sensex started on April 1, 1979 and NIFTY started on Nov 3, 1995.
So SENSEX is 16.6 years elder than NIFTY and has grown very big.
Even if they would have started together, the constiuent stock numbers are different BSE SENSEX 30 Scrips and NSE NIFTY 50 scrips, they would grow differently.