woah just found out the real reason of lot size increase.
SGX nifty 1 lot is $2 i.e approx 130
1 lot SGX nifty Value approx 130* index ~10 Lakh INR
eailrer 1 lot nifty earlier 50 * index ~ 2.5 to 3.5 lakh INR
now 1 lot nifty 75 * index ~ 5~6 lakh INR
becuase of this even though SGX has very less volume but open interest value wise they are almost double/tripple.
This is 2014 statistics before the lot size increase.
No wonder NSE did not like it desperate attempt to salvage some of the damage by lobbying the policy by SEBI.
interestingly the band is suggested at 5 lakh to 10 lakh.
Expect more hike in future lot size till we attain parity with SGX.
Some more info:
SGX nifty minimum tick size is 0.50 comapred to Nifty 0.05
tick value 0.50*130= 65INR vs 0.05 *75 = 3.75 INR
Margin Overnight position 65000 INR vs 45000 INR
Margin percent 6.5% vs 8.1 %
So we can expect the margin to reduce over time till we have parity.