Document reviewers who get their assignments via official temp agencies are among the 2.8 million who earn a living that way. The statistic comes from the research conducted by the National Employment Law Project. Its report is "Temped Out," which you can read here.
But, those 2.8 million are only the tip of the iceberg. Essentially we are all temps. Tenured professors and equity partners are getting the boot just like document reviewers when a project ends.
The search for so-called job security is as foolish a quest as a Baby Boomer like myself chasing a youthful appearance. We may look younger than our age but the world still perceives as a "old" and discriminates accordingly.
As temps, the only sensible strategy to keep working is to seek out, do, and leverage assignments which will get us more work. Doing work solely to receive a paycheck will quickly render us unmarketable.
Demand keeps mututating. To present what the marketplace needs we can only hunt for the kind of work which provides the knowledg base, skills, and contacts employers and clients/customers will pony up money for.
Will robots be doing more and more of document review? If that seems in the near future, then lawyers have to find another niche to focus on. The process to get there could require a short-term reduction in immediate compensation. Or, you will have to pick up another kind of work simultaneously.
As a work issue, this is one of the few in which there is not a generational divide. Members of the Silent Generation, Baby Boomers, and Generations X, Y, and Z are all temps. Assuming otherwise is delusion.