Q:

Do people respond more to $ off promos or % off promos?

In the past we've typically used promotional codes on our site in either banners or other advertisement placed images. And I was wondering if anyone has any information on performance of banners with using Dollar amounts off or Percentage amounts.
For example...
Save $10 off orders of $100 or more
As opposed to 
Save 10% off your next order*
A disclaimer at the bottom of the page would then state:
*10% discount applies to first $100 in your order
I see a few companies in our competition using the 10% with a disclaimer at the bottom and my personal feeling is that it's misleading, but I do believe that with the use of 10% more people are going to click on it and order.

A:

There's a lot of marketing chatter on this topic but there is one main thing to consider; which sounds like the more attractive deal in your * specific case*? 
There's an interesting Donut Hole graph from Dealicacy Showing how both can offer better value to the consumer:

The relative (%) benefit remains constant, while the absolute benefit ($ off) has a complex curve. Logically with the relative benefit it's easy to tell how much of a benefit you're getting; it's always the same, it just scales to what you buy. But with the absolute benefit you always know what you're getting. Never underestimate the power of less thinking.
A marketing study conducted by Evo A/B tested relative vs absolute benefits and found the following results:

$50-Off Coupon generated 170% more revenue than the 15%-Off Coupon.
$50-Off Coupon had 72% higher conversion rate.

I think the issue here is twofold; as mentioned, it's easy to understand how much I'm saving if you say I save $50: I save $50. Additionally, 15% really doesn't sound like much. 
Consider the following bargains, both yielding equal savings on a certain product: 75% off or $5 off. Clearly the value of the relative benefit seems higher. Roughly speaking, a benefit of 40% or more starts to sound pretty significant. A dollar amount of $50 or more sounds significant.
If one value clearly appears to be a better value, it's probably best to offer that option as long as it's not misleading (like the terrible, lying asterisk in your question). Otherwise it would probably be best to A/B test your specific case if there's no clear winner.

A:

Behavioral economics looks at this type of question, and would be a good area for you to investigate. http://en.wikipedia.org/wiki/Hyperbolic_discounting talks about how people perceive discounts. My immediate thought for your specific issue is that people will minimise cognitive load - a % discount requires them to think a bit more than a $ discount, so the greater response is likely to be from a $ discount.

A:

I work in the financial industry and during tax season, this always comes up. Which do we offer: 

20% off, or 
$25 off tax prep? 

Typically our software will calculate the most advantagous and offer that price to the client. With verbal confirmation that they are receiving the best "deal", clients always seem satisfied.
Of course tax preparation can get pricey, so the % off generally wins. But this assurs the client of the most savings either way, without having to calculate each discount on their own for the better deal.

