What a difference a few years makes.

Back in February 2010, Americans over the age of 18 spent a total of ~451 billion minutes’ time on the Internet, according to comScore’s Media Metrix research.

By comparison, in February 2013, the total time spent online had nearly doubled to ~890 minutes.

The vast majority of the increase is attributable to tablet computers and smartphones rather than PCs:

• PC minutes rose from ~388 billion to ~467 billion (+24%).
• Smartphone minutes grew from ~63 billion to a whopping ~208 billion (+230%).
• Tablet minutes grew from zero to 115 billion (tablets didn’t exist in 2010).

In fact, taken together, smartphones and tablets now account for nearly 60% of the time online spent by people age 18 to 24.  On the other hand, smartphones account for a relatively small 25% of time spent online by Americans age 50 or older.

This age divide is also clearly evident in comScore’s estimated breakdown of platform adoption:

All American Adults

• PC only:  ~30%
• “Screen jumpers” (PC + mobile):  ~63%
• Mobile platforms only:  ~7%

Young Adults (age 18-24)

• PC only:  ~22%
• Screen jumpers:  ~65%
• Mobile only:  ~13%

Older Adults (age 50+)

• PC only:  ~48%
• Screen jumpers:  ~51%
• Mobile only:  ~1%

The comScore analysis also provides some interesting stats pertaining to online share of minutes by the type of content being accessed.

Most online time spent on PCs:

• Business/Finance (~68%)
• TV (~68%)
• News/Information (~62%)
• Sports (~62%)
• Retail (~49%)
• Health (~54%)

Most online time spent on smartphones:

• Radio (~77%)
• Social Media (~58%)
• Weather (~55%)
• Games (~48%)

Tablets don’t lead in any single category, but score particularly well in these two:

• Games (~34% of time online is spent on tablets)
• TV (~20% of time online is spent on tablets)

More details and insights from the comScore report can be found here.