Improving Search Ranking for Maps
Search is the core mechanism that connects guests with Hosts at Airbnb. Results from a guest’s search for listings are displayed through two interfaces: (1) as a list of rectangular cards that contain the listing image, price, rating, and other details on it, referred to as list-results and (2) as oval pins on a map showing the listing price, called map-results. Since its inception, the core of the ranking algorithm that powered both these interfaces was the same — ordering listings by their booking probabilities and selecting the top listings for display.
But some of the basic assumptions underlying ranking, built for a world where search results are presented as lists, simply break down for maps.
The central concept that drives ranking for list-results is that user attention decays starting from the top of the list, going down towards the bottom. A plot of rank vs click-through rates in Figure 1 illustrates this concept. X-axis represents the rank of listings in search results. Y-axis represents the click-through rate (CTR) for listings at the particular rank.
To maximize the connections between guests and Hosts, the ranking algorithm sorts listings by their booking probabilities based on a number of factors and sequentially assigns their position in the list-results. This often means that the larger a listing’s booking probability, the more attention it receives from searchers.
