I need information of Demand Side Platforms popular in the U.S. E-commerce market, and the reason why the platforms are so popular with some case studies.

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I need information of Demand Side Platforms popular in the U.S. E-commerce market, and the reason why the platforms are so popular with some case studies.

Demand-side platforms (DSPs) are sophisticated advertising tools which provide the advertiser with real-time data across multiple advertising exchanges and allow for real-time adjustment of the advertising campaign to better reach the intended audience. The return on ad spend (ROAS) is typically 1,500-1,700%, but returns as high as 10,874% have been reported.
Below you will find a deep dive of our findings, including several case studies and a list of recommended DSPs.
DSP OVERVIEW
Until recently, buying an advertisement (even online) required a manual process involving several people. As a result, changing the ad's appearance and/or location could take hours or even days, making it difficult to make the adjustments needed to best reach the target audience, especially if multiple ad exchanges and/or platforms were used. In contrast, demand-side platforms (DSPs, henceforth) manage multiple ad exchanges through a single interface.
This enables marketers to buy ad space in a process called real-time bidding (RTB). "DSPs process bids for ad space, choose the best impression, and then the ad is served in an app." This automated process means "it takes less than a tenth of a second for a DSP to determine the value of an impression to a specific advertiser based on their targeting parameters and secure the ad space."
ADVANTAGES OF DSP
There are many advantages to the advertiser in using DSP. First, the real time access means that the advertiser can receive immediate data on website traffic, page views, impressions, and click-through rates. Not only is the data received in real time, changes to the ad campaign can be made in real time as well, allowing the advertiser to swiftly re-target ads as the patterns of their consumers change.
A quick note on definitions: An "impression" in this context means sending the ad from the server to a user. This is distinct from "reach," which indicates the number of people who have seen the ad. So, for example, if one person sees the same ad three times (that it, it was sent to their device three times), it counts as three impressions, but still has reached only one individual. A "click-through" means that a user has clicked on the ad to be taken to the product or service's site, hopefully to purchase it. The higher the ratio of click-throughs to impressions, the more effective the ad is.
Secondly, a DSP allows all of this flexibility to be achieved "in a single centralized system" rather than the advertiser having to personally maintain multiple ad servers. Access to multiple ad exchanges ensures "that your campaign reaches out to all niches which may possibly be relevant, leaving no digital stone unturned."
The third advantage of using a DSP is that most offer a flat monthly rate, which means that the costs are fixed for the advertiser, which makes budgeting easier. At the same time, a properly-managed DSP will give a higher return on investment (ROI) by keeping advertising money "from being wasted on exposures that guarantee little to no returns. Instead of just putting your ads anywhere, DSPs will decide which impressions are most valuable to your campaign."
EFFECTIVENESS OF DSP (CASE STUDIES)
The above advantages make DSPs extremely effective. One case study by SRAX states that their average ROAS (return on ad spend) is 1,767%, but that their highest ROAS is 10,874%. They also reported an average sales lift of 5.4%, but that some of their clients had reported sales lift of up to 20.36%.
For another case study, Cybba offers a DSP platform as well as expertise in using it to best effect. They partnered with Telecharge, "the official box office for Broadway and off-Broadway theatre tickets." Telecharge had no shortage of traffic (230,000 unique visitors each month) but these visitors were not converting into sales. Cybba used Telecharge's existing customer data to create a targeting strategy, which "generated nearly 24,000 conversions across 58 shows, translating to an estimated $6 million dollars in ticket sales."
A 2016 case study from MediaMath detailing their partnership with Luisa Via Roma further cements the effectiveness of using DSPs. They used a DSP with decisions guided by a data management platform (DMP). The reported results include an 1170% boost in ROAS/ROI and the increase of Luisa Via Roma's marketing investments on the basis of those returns.
Finally, we offer the case-study of the partnership of Ray Ban (the sunglasses manufacturer) with Rakuten Marketing. This particular example comes from outside the US, but due to being the most detailed case study in terms of detailing the results, we thought it useful to present: Rakuten provided a cross-device DSP and delivered "relevant and engaging HTML 5 ads to Ray-Ban’s target audience" and tracked customer behavior throughout, optimizing and refining the ad campaign throughout. The result was an ROAS of 15:1 (1,500%) and a mobile-only ROI of 4:1, with the overall performance exceeding the ROI goals by 275%.
MULTIPLE VS SINGLE ITEMS
We are not entirely certain how "multi-items and single items" should be understood in the context of the question. If the question merely refers to the number of products or services being sold--e.g., a company that sells a variety of items vs. one that sells a single service such as loan refinancing--we were unable to locate any case studies of a DSP being employed for a "single item" company despite an extensive search. If something different is meant, that we would need clarification to research further.
DSP SERVICES
There are literally dozens of DSPs to choose from. However, Blognife recently released their "Top 10 Demand-side Platforms" list for 2017, recommending MediaMath (noted above in our case studies), TubeMogul, AppNexus, The Trade Desk, Rocket Fuel, BrightRoll, DataXu, DoubleClick Bid Manager, One by AOL, and AppLift. For your convenience, the above links will take you to the homepages of each of these platforms, except for RocketFuel, which due to controversy over some of its practices, was recently shut down by its parent company, Sizmek.
CONCLUSION
DSPs are clearly an incredibly effective tool in online marketing, offering enormous advantages over static advertising and a very high return on investment.

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