If you've picked up the phone only to hear the start of an automatic recording, you're not alone. Roughly 16.3 billion of these calls have been placed just in the first five months of 2018, according to the YouMail Robocall Index. In May, Americans received about 4.1 billion robocalls. That's over 12 calls per person, according to YouMail, a company that, in addition to compiling the database, also offers solutions to the problem. And the number of calls keeps growing. In fact, over the past year, the number of robocalls has almost doubled. A big driver of that increase is the fact that consumers are not answering the phone, Alex Quilici, CEO of YouMail, tells CNBC Make It. "This causes both good and bad robocallers to make even more calls to try to get through — as well as the scammers continuing to make more and more calls," he says.

That's right, robocalls can be legitimate, too. For example, your pharmacy may send you an automated call letting you know a prescription is ready. Totally legal. There are also spam calls you may get from charities and political organizations. Those are legal too. But then there are scam calls, in which fraudsters will illegally call you and attempt to get your credit card number using a fake sales pitch or even a threat. Scams like those selling health insurance and those involving phony IRS bills are among the more common ones, Quilici says. While you probably can't avoid all robocalls (and remember, some can be useful), you can take steps to reduce the number you receive.

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