Counting lines in a file containing exact fields

[Lucy Premus <lpremus@METLIFE.COM>]

Is there a korn shell function to count lines in a file that have one field
thats the same.  For example, if my file looks as follows:

server1   NYHO
server2   NYHO
server3   NYHO
server4   RISC
server5   RISC
server6  NYMLB
server7  NYMLB
server8  NYMLB
server9  NYMLB

I want the script to read the file and count up that there are 3 NYHO, 2 RISC,
and 4 NYMLB.  However theres a catch, in reality my files will be much larger
than this containing much more than 3 different instances.  I don't want to have
to compare each line to the literal (ie. NYHO, RISC or NYMLB) because theres
just too many of them.  Is there any easier way?