The Scrabble theory is used to describe economic complexity for countries. “Letters” can be equated to “expertise” and “combinations” can be equated to “innovations”. The theory dictates that the more letters a country has, the more combinations it can create. The increase in combinations in relation to number of letters is exponential. 7 letters equals 584 possible combinations..
Of course, certain letters have higher scores (ie: Q), and you want more of those in your system, although by definition they are scarce.
Note: An Original Source For the Theory BOOK (with the scrabble phrasing): http://atlas.media.mit.edu/book/ and PAPER (with a lego phrasing): http://chidalgo.com/Papers/HidalgoHausmann_PNAS_2009.pdf