http://en.wikipedia.org/wiki/Panic_of_1819 http://en.wikipedia.org/wiki/Panic_of_1819 http://en.wikipedia.org/wiki/Panic_of_1837 http://en.wikipedia.org/wiki/Pa

http://en.wikipedia.org/wiki/Panic_of_1819 http://en.wikipedia.org/wiki/Panic_of_1819 http://en.wikipedia.org/wiki/Panic_of_1837 http://en.wikipedia.org/wiki/Panic_of_1837 http://en.wikipedia.org/wiki/Panic_of_1857 http://en.wikipedia.org/wiki/Panic_of_1857 http://en.wikipedia.org/wiki/Panic_of_1873 http://en.wikipedia.org/wiki/Panic_of_1873 http://en.wikipedia.org/wiki/Panic_of_1893 http://en.wikipedia.org/wiki/Panic_of_1893 http://en.wikipedia.org/wiki/Panic_of_1901 http://en.wikipedia.org/wiki/Panic_of_1901 Almost every 20 years, like clockwork.