Smart software and robots are not poised to wipe out large numbers of American jobs, but technology-driven automation will affect most every occupation and can change work, according to new research from McKinsey.

The report, published on Friday and written by two members of the McKinsey Global Institute, the consulting firm’s research arm, and another McKinsey employee, adds a twist to the debate over the likely nature and pace of automation in the workplace.

Today’s automation fears essentially rest on two assumptions. First, the speed of advances in digital software and hardware is faster than in previous waves of technological change. And second, clever software and machines are increasingly able to automate cognitive tasks, not just physical ones. Artificial intelligence, it seems, poses a new kind of threat to jobs — not so much replacing muscle but brains.

Looking at the trends in artificial intelligence, Carl Benedikt Frey and Michael A. Osborne, researchers at Oxford University, estimated in a paper published two years ago that 47 percent of American jobs were at risk from automation.

The McKinsey research suggests a different kind of impact, at least over the next three to five years, which is the time span of its analysis. The McKinsey study found that less than 5 percent of jobs can be entirely automated using “currently demonstrated technologies,” which it describes as technologies that are either in the marketplace or in research labs.

Instead, the new research focuses on work below the occupation level, down to some 2,000 different types of work activities in some 800 occupations, using the definitions of a project sponsored by the Department of Labor. Applying that lens, the researchers concluded that 45 percent of work activities could be automated, which could affect people in many different roles.

The work ripe for automation is not just routine tasks in lower-paying jobs. “Most high-wage, high-skill jobs have a significant amount of activity that can be automated,” said Michael Chui, a principal at the McKinsey Global Institute, and a co-author of the report.

Jobs where some portion of activities could be automated include physicians, financial managers and senior corporate executives. At the apex of the corporate job ladder, chief executives, more than 20 percent of the work could be automated, McKinsey estimates. The C.E.O. chores that could be automated with machine-learning software include analyzing reports and data to make operating decisions, preparing staff assignments and reviewing status reports.

Landscapers and home health care workers are among the occupations less susceptible to automation than chief executives, according to McKinsey.

The value of the McKinsey research, experts said, is that it provides a fine-grained analysis of the impact of automation.

“It makes a lot of sense to look at automation at the task level, as a way to think about redefining jobs,” said Erik Brynjolfsson, a professor at M.I.T.’s Sloan School of Management and co-author of “The Second Machine Age: Work, Progress, and Prosperity in a Time of Brilliant Technologies.”

The McKinsey authors emphasized the potential for automation to enrich work, liberating people to focus on more creative tasks. Apparently there is a lot of room for improvement on that front. According to one calculation in the report, “just 4 percent of the work activities across the U.S. economy require creativity at median human level of performance.”