The latest estimate I read is that there were 3.4 billion robocalls in the month of April 2018 in the U.S. -- an increase by almost 900 million a month compared with a year ago.
They use software and devices that scroll through random numbers at astronomical speed, so in most cases they have no idea who they're calling.
Seeing our own number on the caller ID is an old spoofing trick -- the newest changes sense the typical area code of the location being called and spoof that area code to trick us into thinking it's local.
It's here and it's escalating because people answer and many people fall for the criminal hoaxes which are perpetrated by entities in other countries, who are very hard to find and very hard to prosecute or punish.
I dropped my landline ages ago, and my cell phone doesn't get as many junk calls now. I use the "Hiya" and the "Trucaller" apps and keep them updated, and they do a good job of identifying and warning of -- or blocking -- junk. Nomorobo is great, but still not available for everyone.
Best bet is to stay up-to-date on articles about the issue and also about the behavior and technology we can use to try and protect ourselves; continue to be vocal to the powers-that-be; and warn the people we care about so they won't fall prey to the scumoftheearth who perpetuate this despicable trickery.
Few things reveal your intellect and your generosity of spirit—the parallel powers of your heart and mind—better than how you give feedback.~Maria Popova