With the use of AdWords for instance, broad and exact matching of keywords can be used to make these figures effective.
1st rule will be: Authors should make sure that all keywords appear in same ad group as broad and exact matches--allowing complete control over what keyword click you are paying for and how you monitor your keyword results. If the keywords is web marketing for example, you know a visitor must have typed in that exact phrase.
2nd rule will be: There should be maximized stem versions and plurals of keywords--separating the broad and exact words, the word web design over web designs will be accurately tracked in terms of converting while also depending on what you are selling.