Despite the tough economic environment and unprecedented challenges to the industry, consumers' use of digital media climbed to new heights in 2009 as the Internet continued to evolve as an integral component of Americans' personal and professional lives, according to data from comScore.

Below, findings from the comScore 2009 US Digital Year in Review, which summarizes recent digital marketing trends and discusses implications for 2010.

Search: Google and Bing Led Market Share Growth

The introduction of Bing in June 2009 enabled Microsoft to gain renewed traction in the search marketplace: During the course of the year, Microsoft Sites grew from 8.3% to 10.7% share of all search queries, with nearly all of the growth coming in the second half of 2009, subsequent to Bing's introduction.

However, despite the new engine's initial gains, Google Sites continued to hold a strong lead in the US search market, accounting for 65.7% of all searches in December, up 2.2 percentage points from a year earlier.

The US core search market grew 16% in 2009, driven by gains in the number of unique searchers (6%) and search queries per searcher (10%).

• Google Sites' search query volume grew 21%, driven both by gains in searches per searcher (up 10%) and unique searchers (9%).
• Microsoft Sites had the largest growth in search volume (49%), propelled by gains in both unique searchers (15%) and searches per searcher (30%).
• Ask Network's search query volume grew 12%, driven mainly by attracting more searchers (up 19%).

Social Networking: Facebook and Twitter Surge, MySpace Refocuses on Entertainment

Social networking continued to gain momentum in 2009, with nearly four out of five Internet users visiting a social networking site on a monthly basis, and Facebook and Twitter propelling much of the growth in the category.

• Facebook surged to the No. 1 position among social networks for the first time in May and continued its strong growth trajectory throughout the year, finishing with 112 million visitors in December 2009, up 105% for the year.
• Twitter finished the year with nearly 20 million visitors to its website, up from just 2 million visitors the previous year. Much of Twitter's audience growth occurred during the first few months of 2009, at one point jumping from 4 million visitors to 17 million (between February and April).
• Although the 2008 category leader MySpace experienced some declines in audience, a new strategic focus on entertainment content achieved some success: MySpace Music increasing 92% percent during the year.

Meanwhile, MySpace's user composition shifted toward younger audience segments in 2009; people age 24 and younger now comprise 44.4% of the site's audience, up more than 7 percentage points from the previous year.

Facebook's audience, by contrast, was evenly split between those younger and older than age 35. The most noticeable demographic shift on Facebook during the year occurred among adults age 25-34, who now account for 23% of the audience, up from 18.8% last year.

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Twitter's Demographic Composition

All demographic segments of Twitter users recorded substantial gains, but certain segments grew more rapidly than others.

The initial success of Twitter was largely driven by users age 25-54, who comprised 65% of all visitors to the site in December 2008, with those age 18-24 accounting for just 9%.

Despite Twitter's initially older skew, as it gained widespread popularity with the help of celebrity Tweeters and mainstream media coverage younger users flooded to the site in large numbers during the year, with those under age 18 (up 6.2 percentage points) and those age 18-24 (up 7.9 percentage points) the fastest-growing demographic segments.

E-commerce: 2009 Marks First Year on Record of Declining Growth Rates

Total US e-commerce spending reached $209.6 billion in 2009, down 2% from 2008, and the first year on record with negative growth rates. Travel e-commerce spending dropped 5% to $79.8 billion, while retail (non-travel) e-commerce spending remained virtually flat at $129.8 billion.