To compute each day typical rates, KAYAK takes all rates for each day ahead of departure over the past yr for flights from Fort Lauderdale to Atlanta, removes the top 0.1% to account for outliers, after which will take the average of every one of the values for each month. https://whitemagictravels.co.uk/blog/what-are-the-things-you-should-know-when-business-class-flights-to-australia/