Dr. Thies Lindenthal formerly of Sedo and now a lecturer at Cambridge University, wrote a paper titled, Monocentric Cyberspace: The Primary Market for Internet Domain Names,
There is some interesting data and Lindenthal does touch on new gtlds as well.
Alexis Kramer gave some analysis and key takeaways.
For Lindenthal, having to type out a long URL is analogous to having a long commute. The more someone has to type, the less likely they are to go to the domain, a tendency that depresses the desirability of longer domain names.
To show that demand was lower for longer names, Lindenthal studied the use of popular U.S. surnames and city names as keywords within longer domain names, using examples such as smithfamily.com or newyorkpizza.com. Controlling for how common the surnames are, Lindenthal found that six-letter surnames were 24 percent more likely to appear in a domain name than seven-letter ones.
Lindenthal said the domain name market could be up to 25 percent larger if more high-quality domain names were available. New top-level domains may help bridge that gap, he said, but with a caveat. While they increase the number of shorter names available, they also introduce an additional keyword—the right-of-the-dot portion of the “notcom” domain—and adding keywords is only viable in the most crowded parts of the domain name space, he said.