The Economist wants to go from selling ads based on time to actually creating branded content using attention-based metrics, but its peers aren’t sure it’s the digital publishing metric of the future. The publisher has joined the likes of the Financial Times and The Wall Street Journal in measuring not just whether an ad is seen or not but for how long. What makes “Attention Buy” foray different is that it’s the first to offer advertisers the opportunity to buy those slices of attention in-app and online.