Web Site Traffic: Search Engine Optimization

D (demand) = No times term is searched for
(see Google AdWords Keyword Tool)
S (supply) = No of sites matching term (eg on Google)
V (value) = Monetary value of term to you, eg per click
P (specificity) = % RELEVANT sites in to 20 (or 50) of Google search
Q (quality) = % GOOD sites in top 20 (or 50) of Google search (ie, how many compete against you?)

Keyterm Value (to you) = (D x V x P) / (S x Q)

Above advice developed from information found in
Ken Evoy's Affiliate Masters Course from SiteSell.com