Over five randomly chosen days this month, a cellphone was taken from a woman on Rockville Pike in Montgomery County, a man on Westway Lane in Prince William County, a man on West Glebe Road in Arlington County, and a woman on I Street NW in the District.

A recent Consumer Reports survey suggests that those four Washington area robberies are part of a huge upsurge in the number of such crimes across the country.

On Thursday, Consumer Reports posted a projection — based on its survey — of the number of smartphone thefts committed last year in the United States. The publication said on its Web site that about 3.1 million Americans were victims last year of smartphone theft.

That, according to Consumer Reports, is nearly double the number indicated by a survey in 2012.

Such figures appear roughly in line with both day-to-day crime reports in the Washington area and crime statistics compiled in the area.

A recent Metro report listed 643 “snatch” thefts in the transit system last year, 90 percent of which involved cellphones. The figure was up from 491 reported in 2012.

The increasing popularity of smartphones, easy to carry and conceal and highly valuable, is a major factor in the growing number of thefts, according to law enforcement officials.

The “prevalence of portable electronic devices, particularly iPhones over the last five years has made the crime of theft/snatch skyrocket,” Metro Transit Police Chief Ronald A. Pavlik Jr. said in the Metro report.

A variety of tactics and techniques have been proposed to protect phone users and reduce the number of robberies and thefts, which are distinct categories of crime. The tactics include promoting increased alertness and prudence among users and employing technological measures to shut down phones that have been taken from their owners, thereby cutting their value.

So far, however, there is little to indicate that the robberies and thefts have declined.

At the end of October, D.C. Police Chief Cathy L. Lanier said phones were taken in about half of the more than 3,400 robberies reported in the city to that point last year. She said the number was about twice as many as six years earlier.

Of the robberies reported on the five days this month, the first occurred in the 200 block of Rockville Pike about 5:40 p.m. April 5 when a man asked to borrow a phone to call his mother and then fled with it. The fourth came about 8:15 p.m. April 9 as a woman looked at pictures on her phone in the 300 block of I Street. A robber snatched it and fled.

At least one person has been arrested in one of the four robberies.

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