Tom note: Here is the fourth entry in our 10 Long March posts for 2018, the 7th most-read item of the year, which originally ran on April 23,  2018. These posts are selected based on what’s called ‘total engaged minutes’ (the total number of time spent reading and commenting on an article) rather than page views, which the T&P; editors see as a better reflection of Long March reader interest and community. Thanks to all of you for reading, and for commenting–which is an important part of this column.