If you find the topic interesting, then I recommend reading an absolutely delightful paper written a few years ago for a Canadian commission of inquiry by one of our elder statement of public admin and government that I’m proud to call a friend: http://epe.lac-bac.gc.ca/100/206/301/pco-bcp/commissions/oliphant/2010-07-20/english/documents/pdf/reportthomas-en.pdf
The paper concerns the manner in which incoming and outgoing communications are managed at “the center” (in this case, the Prime Minister’s office), but the principles are the same as regards the WH. Much of the data comes from the 2003-2006 period, but the trend is evident. It’ll get ya thinking.
Perhaps equally informative was the defensive manner in which critics responded to the paper: http://epe.lac-bac.gc.ca/100/206/301/pco-bcp/commissions/oliphant/2010-07-20/english/research/policysubmissions.php.htm