decade	# words
-----	-----	-----

1	1810s	1181205
2	1820s	6927173
3	1830s	13774588
4	1840s	16048393
5	1850s	16471649
6	1860s	17054872
7	1870s	18562265
8	1880s	20315965
9	1890s	20600843
10	1900s	22097593
11	1910s	22700638
12	1920s	25653746
13	1930s	24602615
14	1940s	24347955
15	1950s	24544831
16	1960s	23977232
17	1970s	23815191
18	1980s	25315978
19	1990s	27941535
20	2000s	29567390