The 12 jobs most at risk of being replaced by robots

"I don't think it is going to happen next year or the year after, but I do believe that probably by the mid '20s to the late '20s, you'll start to see a dramatic change in sort of how machines run the world," Greg Creed, CEO of Yum Brands, told CNBC.

Yum owns a handful of fast-food companies including KFC, Taco Bell, and Pizza Hut.

The fast-food industry is already using technology to supplement or replace human workers through the use of tablets and smartphone apps that allow customers to order their food without interacting with any employees.

But robots and "smart" computers aren't just threatening the jobs of fast-food workers.

They could replace up to half the US workforce within the next decade or two, according to an Oxford University study from 2013.

The study identified more than 700 occupations at risk of computer automation.

Here are the jobs that are most at risk, based on the study.