What determines "ranking" of clips?

I have just recently started uploading clips, and am wondering what determines whether your clip appears on page 1 or page 8 of a simple search? Traffic, for example.

Is it random? Apparently not chronological or by sales. Or is there a secret formula that those who have discovered would rather not share?

As one who has also bought numerous clips on Pond5, I personally don't mind skimming through a zillion clips, but I know others do.
Thanks!
-Bob

There is an artist forum section down below, but I will try to answer your question. Default searches are based on a complicated algorithm were the variable of completed sales has the most importance. Clips that sell have a better chance to be in the top position.