A small but growing number of Americans are opting to cut the cord on their traditional phones and rely solely on mobile phones, mothballing their curlicue-corded phones next to other quaint relics such as black-and-white TVs and LP records.

Roughly 4 percent of households nationwide have made the switch to all wireless, up from 3 percent a year ago, according to Yankee Group, a telecommunications consulting company in Boston. That percentage is expected to swell to 15 percent in the next five years.

Since the nation’s first commercial cellular phones hit Chicago 20 years ago, the phones have moved from status symbols of the rich to necessities of modern life along with cars and PCs, especially for the young and mobile. Today, roughly half the country’s population — about 140 million — has a wireless phone, up from 38 percent three years ago, according to Yankee Group.

Among the 18-24 age segment, a hefty 12 percent has ditched fixed-line phones in favor of wireless.

“The traditional phone line as we know it is on its way out,” said Jeff Kagan, an Atlanta-based independent telecom analyst. “The only reason we’re still tied to our homes and offices with wireline phones is because that’s the way it has always been. We like the freedom of wireless, but a transition has to take place. It’s a behavioral change and that always takes time.”

Better rates

Declining costs have been a big impetus for many early adopters of all-wireless service.

The price winds started to shift in the late 1990s, when AT&T Wireless announced the first calling plan offering a “bucket” of minutes at a fixed cost, instead of the standard per-minute rate for every call. That allowed people to start considering wireless as their main phones.

Until then, people turned off their cell phones to avoid being charged for incoming calls, Kagan said.

Wireless customers are charged for both incoming and outgoing calls.

Also gone are the days when cell phone users paid hefty premiums, some seven to 10 times more per minute, than for conventional service.

A number of analysts now contend that wireless service, with packages that often include unlimited nighttime and weekend calling, is cheaper than landline.

Downside of wireless

Still, there are a number of disadvantages to consider before cutting the cord.

Items to consider when wading through the options

Some are reluctant to give up their landline because of Internet access. But most drawbacks boil down to service, price and safety.

Lousy reception, dropped calls, dead spots and busy signals from overburdened lines remain a problem, but the industry is getting better.

“Wireless companies are doing a much better job providing good coverage, but up until now it’s been pretty bad,” said Carl Hilliard, president of Wireless Consumers Alliance, a nonprofit consumer group in Del Mar, Calif. “You get into the suburban areas, and service gets spotty, but gradually they’re getting better.”

Still, some people can’t use cell phones even in their own homes because of dead spots or poor reception. Radio signals that cell phones use are inherently unreliable, and like the radio in your car, are affected by topography, buildings and weather.

Consumers Union, publisher of Consumer Reports magazine, warns people not to sign a long-term contract unless they’ve tested the phone in the living room, on the porch, in the back yard and other areas where it will be used frequently.