whiteshark: <parisattack: I wonder how Berliner arrived at his evaluations?>
In the intro of chapter 1 he wrote:
"This description of [values of /ws] advantages is based on:
a) 30 years of top US over-the board chess play;
b) The most outstanding record in world-class correspondence chess
c) Extensive experience in implementing these ideas for computer
<Some extra for the synergy of 2Bs?> There is no explicit mention of it in the book.
When reading over this chapter you get an idea of how dynamic these (relative) values are, always depending on the specific circumstances.