Executive assistants once ran the office. Increasingly, the office runs without them.

The decline of what has been a solid career path for women without college degrees has been quiet and gradual, but in magnitude it has mirrored the downturn in blue-collar factory work, economists say.

Technology and automation have chipped away at duties like papers to be filed and landlines to be answered. A new generation of corporate leaders are content to schedule meetings and book flights on their own. Glad to cut costs, companies have culled their administrative ranks, transformed the role for many of those who have managed to hang on and moved some positions to cheaper parts of the country.

More than 1.6 million secretarial and administrative-assistant jobs have vanished since 2000, according to federal data, an almost 40% decline, comparable to that in manufacturing. The losses haven’t garnered much notice. Unlike a plant closing that leaves thousands of Americans unemployed in one go, jobs in a traditionally female sector have evaporated in dribs and drabs.

At the pinnacle of the sector were the executive assistants, a 95% female workforce, according to labor-market research firm Emsi, that could make as much as six figures.