C = 4m + 3v + 2(i-f) - 2a ©

This is an heuristic, a working formula, that indicates the factors that affect conversion rates of web landing pages.  It's a fully educated formula, born of thousands of tests by a very left brained company, Marketing Experiments.  They are a marketing research lab, completely focused on helping marketers optimize marketing communications by testing all reasonable approaches.  They are owned by the MECLABS Group which also owns Marketing Sherpa, another marketing focused company with great research and insights.  Both companies have large followings and offer a large buffet of free content and paid education of great value to the Well Rounded Marketer.

The formula's parameters are as follows:

C = conversion rate
m = motivation of the prospect
v = the value proposition's clarity and power
i = incentive to convert
f = friction in the conversion process (e.g. hard to read)
a = anxiety (e.g. giving out information)
© = copyright :-)

My interpretation of this is that if the multiplier is relatively larger the value it modifies is relatively smaller.  So a given level of anxiety will overcome an equal measure of value proposition.  Value proposition is more powerful than motivation.  Anxiety is equal to the difference of the incentive to convert minus the friction of converting. A given level of anxiety is twice as strong as the same level of motivation.

No matter the weighting, all these contributors and inhibitors to conversion should be addressed in best practice landing page design.  Keep them clean, simple, focused and compelling.  Keep them focused on one desired action.  Give prospects a strong incentive to act promptly. Don't ask for information that is not immediately essential.  (You can always collect more as the nurturing process moves on.) Make sure your privacy policy is easily accessible. Make sure the value proposition is utterly clear.

Here's a simple example where Marketing Experiments tested two versions of a New York Times subscription landing page.  The second had more than 6 times the paid orders than the first just by repositioning the "intro offer" to a "free trial".

Before:

After:

Landing pages performance can be dramatically improved by very simple changes.  Make it a practice to continually experiment with your landing page elements and be sure to track the results.