The number of digital voice assistants in use will grow to 8 billion by 2023, according to a new forecast by Juniper Research.

This would be an increase from an estimated 2.5 billion at the end of last year as smartphone assistants remain the largest platform by volume, due to Google Assistant and Apple Siri.

Juniper defines a digital voice assistant to be “a software program designed with the intent of filling some or all of the role of a personal assistant, given its instructions by the user through the medium of voice interactions.”

The fastest growing voice assistant categories over the next five years are projected to be smart TVs (121%), smart speakers (41%) and wearables (40%).

With the increase in the number of voice assistants in use, Juniper projects that voice commerce will grow to more than $80 billion annually by 2023.

“We expect the majority of voice commerce to be digital purchases, until digital assistants offer truly seamless cross-platform experiences,” stated research author James Moar. “Connected TVs and smart displays are vital here, as they can provide a visual context that is lacking in smart speakers.”

Amazon Alexa is the market leader, according to Juniper.