A 90/10 allocation between stocks and cash is extremely unsuitable for 99,9% of investors Ms. Buffett's age. She is now 68. I am dumbfounded that someone would call 90/10 a "rule of thumb" and neglect to mention how allocation depends on the plethora of factors (age, cash flow needs and value of assets being in the forefront) that we have been taught in the third part of the CFA curriculum.