[astazangasta]

Why this? Why not measure empirically based on how often people follow your first result?

[whistlerbrk]

That approach is prone to creating a positive feedback loop through an order bias.

[elsewhen]

that's why they track what users do post-click. if the user quickly bounces back to the search results page , then the result probably wasn't a very good fit for that particular keyword.

[austenallred]

Click through rate isn't necessarily indicative of quality.

[jjwiseman]

I'm sure they measure that, also.