Pin-down effect in NIFTY options?

Lots of people talk about 'pin-down' effects on underlying instruments as a consequence of large positions on the options market.  I did a prelimnary analysis using NIFTY options data on an eod of day basis (will do a more detailed analysis using intraday data on expiry dat later).. results arent very strong but arent a clear negation either... this should be an interesting area of research for the future..

From 2005 onwards, approx 30%  cases test positive

From 2006 onwards, approx 20%  cases test positive

From 2007 onwards, approx 50%  cases test positive

From 2008 onwards, approx 40%  cases test positive

note that the data ends in Feb 2009.