PHOENIX — It’s hard to miss the dogged technological ambition pervading this sprawling desert metropolis.

There’s Intel’s $7 billion, seven-nanometer chip plant going up in Chandler. In Scottsdale, Axon, the maker of the Taser, is hungrily snatching talent from Silicon Valley as it embraces automation to keep up with growing demand. Start-ups in fields as varied as autonomous drones and blockchain are flocking to the area, drawn in large part by light regulation and tax incentives. Arizona State University is furiously churning out engineers.

And yet for all its success in drawing and nurturing firms on the technological frontier, Phoenix cannot escape the uncomfortable pattern taking shape across the American economy: Despite all its shiny new high-tech businesses, the vast majority of new jobs are in workaday service industries, like health care, hospitality, retail and building services, where pay is mediocre.

The forecast of an America where robots do all the work while humans live off some yet-to-be-invented welfare program may be a Silicon Valley pipe dream. But automation is changing the nature of work, flushing workers without a college degree out of productive industries, like manufacturing and high-tech services, and into tasks with meager wages and no prospect for advancement.

Automation is splitting the American labor force into two worlds. There is a small island of highly educated professionals making good wages at corporations like Intel or Boeing, which reap hundreds of thousands of dollars in profit per employee. That island sits in the middle of a sea of less educated workers who are stuck at businesses like hotels, restaurants and nursing homes that generate much smaller profits per employee and stay viable primarily by keeping wages low.