The advertiser with the largest budget does not automatically win Meta's ad auction. Meta ranks each ad using Total Value, a score based on the bid, the estimated likelihood that someone will take the desired action, and the quality of the ad. A smaller advertiser can therefore outperform a larger competitor by showing a more relevant and engaging ad. In 2019, Meta replaced its single relevance score with three separate measures. Its quality ranking documentation explains how quality ranking, engagement rate ranking, and conversion rate ranking compare an ad with others competing for the same audience. Quality ranking considers signals such as people hiding or reporting an ad. Engagement rate ranking estimates how likely people are to click, react, comment, or share. Conversion rate ranking estimates how likely they are to complete the action the campaign is designed to generate. These rankings can have a direct effect on cost. The ad technology analysts at Segwise report that improving a ranking from Below Average to Above Average can reduce CPMs by 50% or more in a competitive auction. That can make a greater difference than changing the bid. Before increasing the budget of an underperforming campaign, check the diagnostics in Ads Manager. A Below Average ranking often points to a problem with the creative, message, or landing page rather than the amount being spent. Increasing the budget on a weak ad usually buys more expensive impressions without improving its conversion rate. For another explanation of the auction process, provides a useful overview.