The top five retailers in digital marketing in 2015 are just released, ranging from very large to very small size. Spending on digital ads reached $12.91 billion last year, which was far out spacing from other industries, among that paid search alone reached $278.9 million monthly.

Of course those figures don't account for other spending such as consulting, marketing content composition, site optimization, staff time, etc. The time and money scores effectiveness in the main channels: social media, email, paid and organic search.

Below are the merchants that ranked number one in 2015 and a brief summary of why they got there.

1. Best email marketer: Beyondtherack.com

Beyond the Rack gets 16.2% of its traffic from email campaigns. This is approximately five times than other retailers. Its clear that the content of its email is resonable enough to click on.

Beyond the Rack on average sends two emails per day to new sign ups each moth. The retailer clearly communicates to customers often and suggests high premimum on email to drive sales.

The business has three out of four key marketing features. First, the emails are adaptive on mobile. Second, a shopping cart abandonment program runs in place to encourage customers to complete purchases. Finally, a sign up pop up box on the homepage asks new visitors for subscribing their email address to get discount.

2. Best Organic Search: Amazon.com

Amazon leads by organic search and earns the highest points in sale, from the sheer number of natural visits that blows far competition. More than 55 million Amazon.com visitors came per month, which were 662 times higher than the median and five times compared to the second highest Walmart.com 7.7 millions

In an analysis of Alexa, Amazon ranked in the top five results on top keyword search and often scored No.1 in merchandise categories tracked

3. Best Paid Search: The Newyork Times (nytimes.com)

The New York Times Co., selling gifts, photos, and art on its store, spent $1.3 million per month on paid search last year. It was 48 times higher than the median spend including those who don't invest in paid search. The merchant got 19.9% traffic from paid search translating to nearly 24.8 million visits.

4. Best Social Media: Amazon.com

The only reason for Amazon's lead in social media is its sheer size and ability to convert shoppers from social networks. While the merchant gets 1.5% of its traffic from social channels, roughing 14 millions visits, those visitors lead to $1.32 billion in direct online sales, far and away the biggest among the tracked retailers.

Amazon also earns high scores for its followers on Facebook, the seventh big name behind the other brands and entertainment companies like Discovery Channel or Victoria's Secret, etc. But their followers are more engaged than other retailers and that helps it score as well. On average, each post on facebook earns more than 4.7k comments, greater than 7k shares and 213k likes. Each post on twitter is retweeted 274 times on average.