Less than a tenth of a percent of delivered spam is clicked on

MTA Delivery	82,700,000	21,100,000	10,100,000
User Site Visits	10,522	3,827	2,721
	0.01%	0.02%	0.03%

 

Kanich et al of Berkeley and UCSD in ‘Spamalytics: An Empirical Analysis of Spam Marketing Conversion’ have run a trial to calculate the spam conversion rates for three bogus campaigns. I have recalculated the rates based on emails actually delivered.

http://www-cse.ucsd.edu/~savage/papers/CCS08Conversion.pdf