It's hard to interpret a smile, whether you're looking at a human face or a set of equity returns. With that in mind, a key question in the equity markets is whether skew is correctly priced or not. Get it right, and your strategy is set fair. Get it wrong, and somebody else is going to take the gain. With that in mind, we present an exclusive summary of a recent report from Societe Generale that lifts the veil on the causes, behaviour, and consequences of a smile - skew - in the derivatives world.