In the good old days, people worried about killer robots traveling back in time to knock off the mother of humanity's last, best hope. But now something darker is on people's minds: job-killing robots that put our mothers, fathers, and everybody else out of work for good.

That's probably not a blockbuster. But is there any reason to think this actually might happen any more than, say, Skynet launching Judgment Day against us?

Well, if you listen to the pundits and the politicians, it's only a matter of time until it does. Whether it's cars that drive themselves, factories that run themselves, or machines that think for themselves, the idea that we might make human work obsolete has gone from science fiction to something a little less out there. Indeed, robots can already write news stories, analyze financial data for big banks, and even beat the best Jeopardy players in the world. Do you really think you're going to succeed where Ken Jennings has failed? (What is: No).

But, to paraphrase economist Robert Solow, we can see robots taking our jobs everywhere but the productivity statistics. In other words, if machines really were replacing more and more workers, then more and more would be getting done for every hour that humans do work. But that's not the case. Productivity growth has only averaged 1.3 percent the past 10 years, compared to 2.9 percent in the 10 years before that.

So why are people getting so, well, worked up about a robot menace that, at least according to the numbers, doesn't seem to exist? Part of it is probably that AI is still in its infancy, so, even if machines can't do a lot of white-collar work now, it isn't hard to imagine that they will soon as long as computing power continues to grow at the same exponential pace. Oxford academics Carl Benedikt Frey and Michael Osborne think that 47 percent of all jobs are actually at risk of being, in their words, "computerized" in the next 20 years or so. And on top of that, there's the fact that workers really are getting asmaller slice of the income pie than ever before, which is what we would expect if so many jobs were getting automated that more money was going to the people who own the robots instead. Specifically, economists Loukas Karabarbounis and Brent Neiman think that the rise of the machines explains half of this decline of labor.

The last part is more mundane and more speculative. People seem to worry about losing their jobs to robots when there aren't as many jobs to go around. And more than that, it doesn't take a lot for the one to become an excuse for the other. Think about it like this. It's true that we had the biggest financial crisis in 80 years, but it's also true that we had the biggest government response as well. We spent $700 billion bailing out the banks, another $700 billion on tax cuts, safety net spending, and other stimulus, and the Federal Reserve even began printing money after cutting interest rates to zero didn't do the trick. It was about as much as was politically possible. It sure seems like it should have been enough. And yet it wasn't. At least not to jumpstart anything more than a slow and steady recovery that still hasn't reached the people who need it most.

It isn't very exciting, though, to say that as much as we've done, we needed to do more. Politicians don't want to admit it, and pundits don't want to talk about it. Better to say that our problems are the result of too much technology than too little political imagination. And so a few years ago we saw President Obama saying that things like ATMs and airport kiosks were partially to blame for still-high unemployment rather than Republican-forced budget cuts. And one story after another has warned about a post-work future rather than our we-should-be-working present. After all, how many times can you say that the stimulus should have been bigger and that the Fed should have increased its inflation target?

That doesn't mean machines aren't going to take our jobs in the future. They could. But I for one am not ready to accept our new robotic overlords when the last time we were sure they were coming—the 1930s—it turned out that we just had a deeply depressed economy. That could be the case again.