Why does this put 1/2 of items in top chest?

My understanding of hoppers is that things go down before they move horizontally. So everything should go down to the bottom until that chest and hopper are full, then onto the 2nd row up, etc. Instead half the items go to the top chest and half to the bottom. Thanks in advance for any help. I'm on 1.7.2 if that matters.

Solution 1:

It's because your top hopper is pointed directly into the hopper just below it. Point the hopper on the very top to the side, and it will work as you expect.

With the configuration you have, your second hopper from the top is getting 2 items per "cycle". (The top hopper is pushing one item / cycle into the 2nd hopper. The 2nd hopper is pulling one item / cycle from the top hopper.)

Now, the third hopper can only pull one item / cycle from the second hopper, so the second hopper pushes the "extra" item into the top chest.