drop back—
1. fail to maintain one’s position; be outstripped:
- The early leaders drop back and allow others to make the running.
2. go down; decrease:
- The unemployment figures dropped back last month.
drop behind—
1. = drop back 1:
- Don’t drop behind now, just when you’re doing so well.
2. fail to maintain a schedule of payments, etc.:
- If your payments of rent drop behind, you will be asked to leave.
See also: back drop / backdrop.