There’s no knocking search engine marketing off its perch as the kingpin digital marketing channel for retailers.

Retailers earmark about 60% of digital marketing for paid search, according to Internet Retailer estimates in the just-published 2015 Search Marketing 500, an 81-page downloadable report that examines how the biggest and most influential North American web merchants utilize both paid and natural search. The estimate is based on multiple in-depth interviews with web merchants ranked in the Top 500 Guide and the Second 500 Guide.

Paid search budgets are growing. The 500 largest merchants ranked on their 2014 monthly paid search spending collectively upped their spending on pay-per-click advertising by 18% last year over 2013. Amazon, which bids on nearly 3 million keywords, according to Internet Retailer research partner ROI Revolution, increased spending the most, by 56%, among the 500 ranked retailers, while ideeli Inc., a flash sale apparel merchant acquired by Groupon Inc. in January 2014, showed the biggest decrease, a drop of 38%.

Paid search accounts for about two-thirds of the marketing budget at SmartSign.com and sometimes even more. The reason:  the online retailer of printed signs and related products is trying to figure out the best way to get the most out of Google Product Listing Ads. Those ads, which Google introduced in 2012, are retailer listings that Google places in a horizontal display high up on the first results page for a product query. Previous pay-per-click ads were too generic, says CEO Blair Brewster. Now safety managers looking for specific signs such as “Emergency Shut Off” see SmartSign PLAs in bold colors. SmartSign also updated its data feed to Google for PLAs with more specific keywords and descriptions.

By doing a more focused job on paid search from keyword bidding through the landing page, the conversion rate on some products has doubled. “We are spending more but consumers and businesses that click on our PLAs are usually very motivated to make a purchase because they need a sign,” Brewster says.

Paid search analysis is only one aspect of the content in the 2015 Search Marketing 500. Other content includes:

• Data and rankings of the 500 web merchants spending the most on monthly paid search with year-over-year growth, plus the top 10 paid search marketers in each of 15 merchandise categories;
• Competitive data on the 50 e-retailers generating the most traffic from natural search, and the top 10  search engine optimization performers in each of 15 merchandise categories;
• The 25 fastest-growing and 25 slowest-growing e-retailers in terms of search spending, and the 25 web merchants averaging the highest cost-per-click search payments;
• The 50 web merchants with the greatest keyword inventory and the top 10 retailers with the biggest keyword inventory in each of 15 merchandise categories;
  • A comprehensive cover story explaining the rise and impact of Google Product Listing Ads;
  • An infographic summarizing key search engine marketing stats, such as median cost-per-click for the Top 10 paid search spenders by product category;
  • A survey that examines how retailers fight for top natural search rankings;
  • Five search marketing case studies, including a spotlight on Amazon’s growing web services businesses;
  • An overview of top 10 search engine marketing solutions providers, featuring descriptions of products, pricing, number of clients among the top 1,000 American e-retailers and full company headquarters information.

To order the 2015 Search Marketing 500 click here.