How much does the horizontal stabilizer on a 737 move for one unit of trim? Inspired by this question, what exactly is the meaning of a stab trim unit? Is it exactly one degree of stabilizer movement?

The 737 NG FCOMv2 (9.20.9 Flight Controls - System Description) only lists the ranges of the units:


  Stabilizer Position Indication and Green Band
  
  Stabilizer position is displayed in units on two STAB TRIM indicators located
  inboard of each stabilizer trim wheel. The STAB TRIM indicators also display the
  TAKEOFF green band indication.
  
  The trim authority for each mode of trim is limited to:
  
  
  Main Electric Trim
  
  
  flaps extended 0.05 to 14.5 units
  [737-600] flaps retracted 4.10 to 14.5 units
  [737-700] flaps retracted 4.30 to 14.5 units
  [737-800] flaps retracted 3.95 to 14.5 units
  [737-900] flaps retracted 3.90 to 14.5 units
  
  Autopilot Trim 0.05 to 14.5 units
  Manual Trim -0.20 to 16.9 units.
  
  
  The green band range of the STAB TRIM indicator shows the takeoff trim range.
  An intermittent horn sounds if takeoff is attempted with the stabilizer trim outside
  the takeoff trim range.


The full range of travel can be seen as a black arc in the following image (taken from this answer), which could be 17°, but it is hard to say from the image:
The stab trim unit is an offset to the actual horizontal tailplane angle. It is added by Boeing to make the trim value positive.

1STU = 1 degree