The Economist's analysis of Big Pharma's patent cliff woes is worth looking at if only for the accompanying graph and its plunging sales lines for Pfizer's ($PFE) Lipitor, Sanofi ($SNY) and Bristol-Myers Squibb's ($BMY) Plavix, Novartis' ($NVS) Diovan and Merck's ($MRK) Singulair. Report