Despite the popularity of digital-only buyers, many people still rent or purchase movies or TV shows, and they like physical video discs.

In a study of American consumers who buy or rent video, market research company The NPD Group found that 18 percent only shop only for digital content. This is a gain from 14 percent the year before.

Far more people only buy or rent physical media, NPD says: 49 percent shop exclusively for physical discs, a decline from 56 percent the previous year.

That means 33 percent buy or rent both digital and physical media, a gain from 30 percent last year.

Digital's growth comes from heavy shoppers who bought or rented more than four times in the past three months. Only one-third of digital video shoppers completed that many transactions, but they counted for 69 percent of all purchases or rentals.

The most popular online video stores for purchases are Amazon and iTunes, with Google Play and Vudu also finding support. For rentals, Amazon was the leading online store, but iTunes, Fandango Now, and Redbox On-Demand also did well.

"Among consumers who consume both digital and physical video content, the vast majority are still buying and renting physical discs," says Ricardo Solar, senior vice president of video entertainment for NPD.