Saturday’s shooting of Rep. Gabrielle Giffords was so startling in part because of how rare it is that an attempt it made on the life of a major American political figure. Four presidents in history have been assassinated (Abraham Lincoln, James Garfield, William McKinley and John F. Kennedy), with several others (including Gerald Ford and Ronald Reagan) targeted.

Even though they aren’t protected by nearly as much security, attacks on members of Congress are, statistically speaking, rarer. It has been more than three decades since a sitting member of Congress has been murdered. A brief look at the history: