Holiday driving is a terrible thing. Between the stress of added traffic and anxiety about spending hours at a dinner table with obnoxious in-laws, many motorists are in lousy moods.

To make matters worse, a new State Farm study indicates that a growing number of drivers aren't paying attention to the road.

State Farm's annual distracted-driving survey was conducted in July of this year. Responses were collected from roughly 1,000 U.S. drivers 18 years of age and older, all of whom owned a cell phone and drove between one and 80 hours each week.

The survey paints a fairly grim picture of distracted driving in America. Among State Farm's key findings:

The percentage of drivers who access the web on their cell phones has jumped from 13% in 2009 to 21% in 2012.

in 2012. More than half of those who use the internet behind the wheel are updating their statuses on social networks like Facebook and Twitter. That group constituted 9% of all drivers in 2009, rising to 13% this year.

this year. Even checking their news feeds has become more popular with drivers. Today, 15% do so, compared with 9% in 2009.

Not surprisingly, younger, less experienced drivers are the worst offenders. Among those 18 - 29:

A staggering 48% use the internet behind the wheel (up from 29% in 2009)

use the internet behind the wheel (up from 29% in 2009) 30% update their status on social networks (up from 20% in 2009)

update their status on social networks (up from 20% in 2009) 36% check their feeds on those networks (up from 21% in 2009)

check their feeds on those networks (up from 21% in 2009) 43% check their email (up from 36% in 2009)

But let's not lay the blame completely at the feet of younger drivers. State Farm says that as the number of cell phone users has grown, the number of people accessing the web behind the wheel has, too -- and the average age of offenders is dropping.

Ironically, drivers of all ages seem to understand the dangers of distracted driving. Of those surveyed, 72% support laws that prohibit texting and driving, while 45% like the idea of technology that inhibits a driver's ability to use a cell phone. However, nearly two-thirds of those surveyed also believe that current distracted-driving laws aren't useful because they're not properly enforced.

In other words, drivers admit that they have a problem, but they lack the self-control to address it. This may call for a support group.