Traffic
Traffic: reading level, not age
Parents search by what their child can read and by what their child likes: books for a five year old who is just starting to read, board books for a one year old, chapter books for a reluctant reader, a book subscription for toddlers. Age alone is the wrong axis, because two five year olds read very differently. The traffic lever is a page per reading stage with a real explanation of what a child at that stage does with a book, theme and interest pages, an age-to-level guide that answers the query the way parents phrase it, and a subscription page showing sample boxes by level rather than hiding the contents behind a signup form.
