Date: Mon, 1 Jan 2007 18:23:54 -0500 (EST)
From: "Keith F. Lynch" <kfl at KeithLynch.net>
To: WSFA members <WSFAlist at KeithLynch.net>
Subject: [WSFA] Ex-presidents of the US
Reply-To: WSFA members <WSFAlist at KeithLynch.net>

A major topic at last night's New Year's Eve party at the Fabulous
Bungalow was ex-presidents of the US.

I decided it was as good an excuse as any to keep my programming
skills from getting rusty.  So I found a table of presidents, their
birthdays, inauguration dates, and dates of death, and started coding.

There have been five ex-presidents alive simultaneously on three
occasions:

* From March 4, 1861 to January 18, 1862: Van Buren, Tyler, Fillmore,
  Pierce, Buchanan

* From January 20, 1993 to April 22, 1994: Nixon, Ford, Carter,
  Reagan, Bush

* From January 20, 2001 to June 5, 2004: Ford, Carter, Reagan,
  Bush, Clinton

There have never been six.

There are currently three: Carter, Bush, and Clinton.

There have been zero on six occasions:

* Before April 30, 1789, when nobody had ever been president
* From December 14, 1799 to March 4, 1801, when Adams was president
* From July 31, 1875 to March 3, 1877, when Grant was president
* From June 24, 1908 to March 4, 1909, when Roosevelt was president
* From January 5, 1933 to March 4, 1933, when Hoover was president
* From January 22, 1973 to August 4, 1974, when Nixon was president

Washington was the only president to have no ex-presidents alive
during *any* part of his presidency.

My first thought was that the number starts at zero, increases
whenever a president leaves office without dying, and decreases when
an ex-president dies.  But then I realized this wasn't quite right.
Can you see the flaw?

The average number of living ex-presidents in the 19th century was
2.19, in the 20th century was 1.89, and in the 21st century so far,
4.56.  The medians were 2, 2, and 5 respectively.

What about past, present, and future presidents alive at once?  (Of
course I have to exclude anyone who has still not yet been president.)

Nineteen past, present, and future presidents were alive
simultaneously from March 18, 1837, when Grover Cleveland was born, to
April 4, 1841, when William H. Harrison died, and again from January
29, 1843, when William McKinley was born, to June 8, 1845, when Andrew
Jackson died.

The smallest number of past, present, and future presidents were alive
simultaneously, excluding 1784 and earlier, and excluding 1969 and
later, was nine, from Grover Cleveland's death on June 24, 1908 to
Lyndon Johnson's birth on August 27 of the same year.

Another question is when each president was or will have been dead for
as long as he was alive.  Here are all the presidents in order of that
date.  Note that only one president doesn't land in or after the 20th
century.  And that Ford almost made it to the 22nd century.

George Washington     10/06/1867
James K. Polk         01/27/1903
James Monroe          09/08/1904
William H. Harrison   05/28/1909
Thomas Jefferson      09/24/1909
Zachary Taylor        02/21/1916
John Adams            03/08/1917
Abraham Lincoln       06/15/1921
James Madison         10/11/1921
Andrew Jackson        09/02/1923
John Q. Adams         10/07/1928
James A. Garfield     07/22/1931
John Tyler            11/09/1933
Franklin Pierce       08/24/1934
Andrew Johnson        03/02/1942
Martin Van Buren      03/12/1942
Chester A. Arthur     01/02/1944
James Buchanan        07/11/1945
Millard Fillmore      05/07/1948
Ulysses S. Grant      10/19/1948
William McKinley      04/29/1960
Rutherford B. Hayes   05/04/1963
Benjamin Harrison     10/03/1968
Theodore Roosevelt    03/17/1979
Grover Cleveland      09/30/1979
Warren G. Harding     04/30/1981
Woodrow Wilson        04/19/1991
Calvin Coolidge       07/08/1993
William H. Taft       08/28/2002
Franklin D. Roosevelt 06/22/2008
John F. Kennedy       05/17/2010
Lyndon B. Johnson     06/19/2037
Dwight D. Eisenhower  09/09/2047
Herbert Hoover        12/30/2054
Harry S Truman        08/14/2061
Richard M. Nixon      08/03/2075
Ronald W. Reagan      10/03/2097
Gerald R. Ford        06/09/2100

If there's any interest, I can easily modify my programs to do the
same with any other list of people whose birth and death dates are
known, or to list when they'd been dead twice as long as they'd been
alive, or the midpoint of their life, or whatever.