If you think your phone rang more often this year, you're probably right.

Robocalls to Minnesotans doubled in 2018, to an average of eight machine-made calls a month.

"It's irritating as hell," said Lakeville resident Leonard Sims, pausing after lunch in the Minneapolis skyway. "I just got two while I was standing here."

Federal and state regulators are trying to rein in the deluge of calls, which totaled more than 5.1 billion nationwide this year, according to YouMail, a California company that offers a robocall-blocking app for cellphones.

But they're no match for fast-moving advances in technology, which have made robocalls easier and cheaper to make than ever. Some robocall operations have been single-handedly responsible for as many as a billion calls a year.

"They're incredibly frustrating, obviously," said Ben Wogslund, a spokesman for Minnesota Attorney General Lori Swanson. "The technology has gotten so much better.

"One of the problems is, most of these robocalls are coming from criminal enterprises."

Robocallers often bypass the federal "do not call" registry and can easily disguise their own phone number, a practice called "spoofing." By using a false number that displays from the same area code as the recipient — or even appears to be the number of a friend or family member — robocallers can induce a reluctant recipient to pick up their calls.

Minneapolis resident Rosey Coryn is originally from Iowa, but hasn't lived there for years. Yet her cellphone regularly rings with calls from Iowa area codes: robocallers hoping she'll pick up their call.

More than half of all Americans reported getting at least one robocall a day, according to a nationwide survey by Clutch, a Washington, D.C.-based firm that analyzes business data. More than 93 percent said they get at least one robocall a month.

Good news for bad guys

Consumers have the right to block robocalls. Telemarketing sales calls with recorded messages are generally illegal unless you've given the company written permission to call you, according to the Federal Trade Commission (FTC).

But as voice-over-Internet protocols and sophisticated calling programs came into use, it became simple for fraudsters and scammers to make millions of calls from a single computer, routing them around the world and hiding their origin. Basically, it became so easy to break the law that crooks figured they had little to lose.

"The automation has been all on the side of the bad guys," Henning Schulzrinne, a Columbia University professor of computer science, told an FTC conference on fighting robocalls. YouMail estimates that nearly two-thirds of the robocalls targeting Minnesotans are either scams or illegal telemarketing. Truecaller, a Swedish company that makes phone security software, estimated that 22 million Americans lost a total of $9.5 billion to phone scams in 2017, an average of $430 a victim.

The most common illegal robocalls are for financial services: credit card offers, loan consolidation, extended warranties and debt collection. Health care and insurance robocalls are also major offenders, along with timeshare offers.

Some robocalls are allowed, including political calls, surveys and charitable solicitations — if they come directly from the charity and not a third party. Also allowed are routine calls from local institutions such as schools and health care providers — alerting you that your child's bus won't be running, or reminding you of a medical appointment.

In fact, the top robocaller in Minnesota's 507 area code is the Mayo Clinic. In the 612 area code, the No. 2 robocaller is the Minneapolis Public Schools.

State attorneys general, including Swanson, have fought to make phone carriers take more responsibility for cutting down on robocalls. After petitioning the federal government, Swanson and 38 other attorneys general succeeded in getting new rules enacted that allow phone companies to block obviously false numbers before the calls even reach consumers.

Self-help is necessary

Government regulations and aggressive action by phone carriers can help fend off robocalls. But consumers also must play a role, said Alex Quilici, chief executive of YouMail.

"View it like we view the antivirus problem," Quilici said. "Once people got antivirus programs on their computers, the problem became much less." It's a similar story with e-mail spam, he added, which "drove everybody nuts" until spam filters came into widespread use.

"Once everybody has a robocall-blocking app on their cellphone, that will help the problem immensely," he said. The FTC, while not endorsing any specific call-blocking apps, also recommends consumers consider using them on their phones.

People have to rethink their relationship with their phones, Quilici said.

"Consumers have been very used to trusting the caller ID, trusting the number, trusting the person on the other end of the line," he said. "They can't do that any more."

Quilici advises people not to answer calls from numbers they don't know.

"You also have to get out of the habit of automatically calling [missed calls] back," he said.

"Consumers have got to stop answering unknown numbers and they have to do some research before they call numbers back."

That approach is working for Justine Simon.

"I think I get less robocalls than other people," said Simon, of Maple Grove. "If I don't know the number, I don't answer.

"That's my secret."