Above all, specify how shrinkage is measured. Linear dimensions, area, or
volume.  For example how much shrinkange in a blcok whose original
dimensions were 2 cm X  4 cm = 8 sq cm, that now measures 1 cm X 2 cm = 2
sq cm? Looking at the linear dimensions, one would conclude that it was
now half as large as the original and therefore that shrinkage was 50%,
However, its area shrank from 8 sq cm to 2 sq cm, indicating that it is
now 25% of its former size and that shrinkage was 75%.

Measuring volume would probably be the most accurate, but it
obviously isn't  practical for embedded blocks.

BTW, critical point drying of SEM specimens can be a GREAT shrinker!

As others have pointed out, shrinkage also depends on the tissue
involved, and on all the processing solutions it goes through.  Ideally,
every discussion of shrinkage should specify the tissue, and the time,
temperature, and where applicable, the pH of EVERY processing solution,
starting with the fixative.
--
Paul Millikin
Peoria, IL
millikin@mtco.com