Back when OkCupid used to publish interesting statistics, they showed exactly that. It was dramatic and unmistakable. Male value starts low, gradually rises until about age 30, doesn't change much until about age 50, and then very slowly declines. Female value looks almost like a 1/age plot, starting very high and in a downward plunge. No data was available for females under age 18, but the graph slope suggests that value is higher.