When the Dow Jones industrial average plummeted 508 points in
one unnerving day last week, losing 22.6 percent of its value,
it marked the widely followed indicator's largest-ever
percentage loss - notwithstanding initial statistics from
various news services that indicated otherwise.  The tumble
without a doubt represented the biggest point loss ever in the
Dow average, but a larger percentage loss appeared in a table
and article in The New York Times reporting on the 10 largest
percentage declines in the average. For Dec. 12, 1914, a decline
of 24 percent was cited, with the average reportedly having
fallen 17.42 points, to close at 54.  Sorting out why that day
did not represent the biggest loss in percentage terms sheds
light on some interesting facts of Dow history.  The change for
that day was calculated on the previous close, but that close
had taken place nearly six months before. The stock exchange was
shut in July 1914 as World War I began, and it did not reopen
until Dec. 12 that year. The close on