ragazzi è un mistero
qui, una tesi
Wilmott Forums - call & put implied volatility
qui, chiarissimo ( ma a scadenza, credo sottointenda)
Answers.com - Is call and put implied volatility for the at the money option are same
qui, grafi con vola diverse e indicati gli spread den-lett pue e call
Option Chain Implied Volatility Calculator and Dynamic Display Engine
qui un paper ( beh , lo abstract) chiarissimo che sono diverse nella realtà, anche se in teoria non dovrebbe essere
Joint Modeling of Call and Put Implied Volatility
c'è il download
se riesco, lo leggo
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ma ho sonno
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ma mi ha già convinto
The reason behind the inequality of put and call implied volatilities may lie in the
different demand structure for calls and puts. There is an inherent demand for put
options that does not exist for similar calls, as institutional investors buy puts regularly
for purposes of portfolio insurance. There are often no market participants looking to sell
the same options to offset this demand, meaning that
prices may need to be bid up high
enough for market makers to be willing to become counterparties to the deals. With no
market imperfections such as transaction costs or other frictions present, option prices
should always be determined by no-arbitrage conditions, making implied volatilities of
identical call and put options the same.
quindi
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la differenza tra le due IV è un indicatore ?