Last click, as a measure for the performance of digital media, was king for most of the Internet era. Now that its reign is over, the industry must work together to ensure a streamlined attribution ecosystem. The accurate valuation of media is essential to the health of the digital advertising marketplace, as is a more efficient media planning and buying process. Our industry has the chance to seize the great opportunity of this new era by facing its immense challenges now, in the early stages of its development. For at least a decade, the last click stood as the default unit of measure for tracking how well various elements of a digital marketing campaign contributed toward campaign goals. Whatever a user clicked on to go the advertiser’s site -- a link, banner, search result, etc. -- got all the credit. A boon for some, an albatross for others, without systems to gain more valuable insights, this overly simplistic practice was the standard. Until now. Recent advances in data processing and analytic capabilities have provided marketers with powerful tools for improving the attribution of value in a digital marketing campaign. No longer are they forced to use the last click. It's now possible to track and analyze the wide range of marketing influences and user actions that contribute toward campaign goals, whether they are direct-response or brand-oriented. This evolution represents important progress for the digital advertising marketplace. However, change is messy. The rule of the last click has been replaced by pandemonium, by competing forces that are no less confusing and intricate than the fight for the iron throne in HBO’s "Game of Thrones." New vendors, models, and techniques for calculating attribution mixed with today's data-driven, hyper-optimized advertising ecosystem have led to confusion and tension in the marketplace. Factors contributing to the chaos include: Competing and conflicting discrete data sets. Marketers, publishers, exchanges, and vendors each perform attribution calculations using their own proprietary data of user events -- and everyone, naturally, is inclined to defend the validity of their own work. This turbulence is similar to the impression-discrepancy issue, only augmented by a lack of universal terminology, as well as the complexity and variety of calculations. An absence of a Pythagorean Theorem equivalent. When it comes to attribution, it's unlikely there will ever be, or should be, standardized relationships between the values of channels. For one campaign and its particular goals, it may be reasonable to weigh display ad clicks higher than Twitter interactions; for another campaign, it might be appropriate to give more weight to specific user actions that signal engagement. A vendor that specializes in attribution modeling must tailor its solution to individual campaigns -- not every marketer, but every campaign -- as each has its own unique media mix and objectives. This level of customization complicates the attribution process, but must be preserved. Efficiencies should stem from better enabling this level of sophistication. How hard it is to talk about attribution. The growing attribution ecosystem is lacking a universal lexicon. This lack of definitions makes it terribly hard for marketers to compare and contrast various models of attribution calculation, and to confidently choose or devise the one that’s right for their specific campaign. When buyers cannot quickly understand what an attribution model provides, their decision-making slows, their certainty in transactions is compromised, and ultimately their dollars go to media that provides an easier-to-understand return on investment. The development of a common language -- and, even more simply, defining what the key common characteristics of attribution calculations are across the ecosystem -- is the most critical step to enabling attribution capabilities that are both efficient and amply sophisticated. We must have the means to compare and contrast methods of valuation in order to truly take advantage of this wealth of models and insight into user behaviors. At the IAB Advertising Technology Marketplace on June 21 in New York City, we will dive into this issue and reveal information that we hope will lay the groundwork for a more transparent and systemized attribution landscape. This is your opportunity to be at the forefront of progress that will lead us, as an industry, toward the more effective use of advertising dollars, which inevitably brings with it higher CPMs and increased ad revenue. When a marketer can identify what’s working and optimize their campaigns accordingly, they’re going to spend more.