That's according to online advertising firm DoubleClick, which found in its second-quarter 2004 E-commerce Site Trend Report that on a year-over-year basis, "carting" frequency -- the likelihood for a site visitor to add an item to their virtual shopping cart -- has risen from 8.3 percent to 9.4 percent.

There's other good news as well. Conversions rates and average order value have increased in the last year. A total of 4.9 percent of e-commerce visits now result in a conversion, which is an increase of 14 percent over last year. The average online order value increased by 15 percent over last year and now stands at $134.01.

The bad news, however, is that the rate of abandoned carts has increased by 24 percent to 57 percent -- up from 45.9 percent a year ago. What's more, online shoppers who abandon their carts are not returning to them with the same frequency that they have in the past. Last year, shoppers who did return to complete a purchase comprised 35.6 percent of sales. This year that number dropped to 26.5 percent.

Abandoned carts represent a significant amount of lost revenue. DoubleClick estimates that for every dollar spent, $4.51 is missed through abandoned carts.

The DoubleClick report also illustrates the importance of on-site search to the e-commerce process. Sales that originated from an on-site search query reported an increase of 47 percent, which translates into an average order value of $110.62. Overall the value of search-initiated sales as a percentage of overall sales is up to 8.4 percent, an 17 percent increase over last year. The report also found the use of onsite search functionality rose 26 percent.

DoubleClick also reported that users seem to be spending less time on the pages they visit, although the number of pages they're viewing is up. The average number of pages per session is up by 12 percent to 11 pages. But they're now spending only 29 seconds per page (down from 32.5 last year) while overall session length has remained "relatively flat" at 4.82 minutes up from 4.78 minutes in 2003.

In DoubleClick's view, the report findings suggest that e-commerce consumers are now more active in the shopping process, which means marketers have even less time than before to capture attention.

"Consumers are looking at more pages, carting more products and converting more often -- so the opportunity is there. said Eric Kirby, vice president of Strategic Services at DoubleClick, in a statement. "Now, it's up to marketers to not only make the shopping experience as engaging as possible, but also to introduce new strategies, such as remarketing to lost prospects."

The results of the report were compiled using data based on "hundreds of millions of unique visitors, tens of millions of online shopping carts and over $1 billion in total e-commerce sales."

Sean Michael Kerner is a contributing editor at sister site internetnews.com, where this story originally appeared.