Q. How are similarity scores calculated?
Similarity scores attempt to compare pairs of players on the basis of their statistical differences.  Each pair starts off
with a total of 1000 points, and points are subtracted based on the following criteria:

For Batters:
  Career   G: 1.0 pts for each difference of   20
  Career  AB: 1.0 pts for each difference of   75
  Career   R: 1.0 pts for each difference of   10
  Career   H: 1.0 pts for each difference of   15
  Career  2B: 1.0 pts for each difference of    5
  Career  3B: 1.0 pts for each difference of    4
  Career  HR: 1.0 pts for each difference of    2
  Career RBI: 1.0 pts for each difference of   10
  Career  BB: 1.0 pts for each difference of   25
  Career  SO: 1.0 pts for each difference of  150
  Career  SB: 1.0 pts for each difference of   20
  Career Avg: 1.0 pts for each difference of .001
  Career Slg: 1.0 pts for each difference of .002

Positional adjustments are accounted for by subtracting the difference between the players' primary positions:
  Career Pos: 240 pts for  C, 168 pts for SS, 132 pts for 2B,
               84 pts for 3B,  48 pts for OF,  12 pts for 1B


For Pitchers:
  Career   W: 1.0 pts for each difference of    1
  Career   L: 1.0 pts for each difference of    2
  Career Pct: 1.0 pts for each difference of .002 (max 100)
  Career ERA: 1.0 pts for each difference of  .02 (max 100)
  Career   G: 1.0 pts for each difference of   10
  Career  GS: 1.0 pts for each difference of   20
  Career  CG: 1.0 pts for each difference of   20
  Career  IP: 1.0 pts for each difference of   50
  Career   H: 1.0 pts for each difference of   50
  Career  SO: 1.0 pts for each difference of   30
  Career  BB: 1.0 pts for each difference of   10
  Career  QS: 1.0 pts for each difference of    5
  Career  Sv: 1.0 pts for each difference of    3

Role adjustments are accounted for by the following:
  If one is a RHP and the other is a LHP, subtract 10 pts.
  If one is a Starter and the other is a Reliever, subtract 15 pts.
  For Relievers, the Pct penalty is halved and is capped at a maximum of 1.5 * (W+L) penalties.


Q. What is the difference between Overall, Through Age, and By Age similarity scores?
Overall scores compare players on their overall career totals.
Through Age scores compare players on their overall career totals through a certain age.
By Age scores compare players on their overall career totals through a certain age, on a year-by-year basis.