About a quarter of the 8.4 million jobs eliminated since the recession began won't be coming back and will ultimately need to be replaced by other types of work in growing industries, according to economists in the latest Wall Street Journal forecasting survey.

While the job market is constantly shifting as some sectors fade and others expand, this recession threw that process into overdrive. Thousands of workers lost jobs as companies automated more tasks or moved whole assembly lines to places like China. As growth returns,...