By now you’ve probably heard that the S&P 500’s back-to-back annual gains amounted to the best two-year advance since the late 1990s. But finding an example of a worse end to a year than the one that just occurred requires going back even further in time. To at least 1952, when data first becomes available for comparable returns. Since then, it’s never fallen more than the 2.6% it lost from Christmas to year-end, data compiled by Bespoke Investment Group show. The closing drop marks only the