This is well known, so it should come as no surprise. It didn’t REALLY surprise me.
We tested a pop-up form to collect new e-mail newsletter subscribers for our e-commerce site. The one on the right out performed the one on the left. No brainer. What was a surprise, to me anyway, was HOW MUCH the one on the right out performed the other.
Without getting into too many specifics… Compared to the same page without a popup, the one on the left ended up hurting the page’s conversion rate by a very noticeable amount. The one on the right ended up lifting conversion by an even greater margin. The swing was tremendous. Almost 4 times as many people filled out the form on the right (and sales from the simplified popup increased at a significant rate too).
This highlights how usability and the perception of the form can greatly influence performance. With a quick first glance, the form on the left looks overwhelming even though only the e-mail address is required (albeit 2x). The form on the right, easy peasy. And yes, we have ensured the e-mail addresses entered are valid (very high delivery rate).
End result of test. Form on left, disaster. Form on right, big success.