Greg Mankiw has a talent for cutting to the chase when it comes to observations of macro and finance and he doesn’t disappoint in his latest NY Times column, which summarizes his view on how to answer the question: What stocks should I buy? The Harvard professor explains that the best response is not to answer at all, at least not directly. An “evasive” explanation, however, is worth a lot in this case. He advises that “the market processes information quickly”, “price moves are often inexplicable”, and “diversification is essential”. Agreed. Mankiw’s writing about stocks, but his succinct guidelines on equities apply to asset allocation too. For all the reasons that holding a low-cost basket of stocks (i.e., an index fund) is appealing from empirical and theoretical perspectives, the same is true for a multi-asset class portfolio. This is old news, of course, but Mankiw’s column reminds that it’s also forever new in the otherwise hazardous business of dispensing investment advice.