Popularity in the United States (by decade)
Numbers
| Lou (feminine) | Lou (masculine) | |||||
| Year | Rank | Percent Used | Rank | Percent Used | ||
| 2020 | - | - | - | - | ||
| 2010 | - | - | - | - | ||
| 2000 | - | - | - | - | ||
| 1990 | - | - | - | - | ||
| 1980 | - | - | - | - | ||
| 1970 | #1418 | 0.005 | #1846 | 0.002 | ||
| 1960 | #563 | 0.016 | #1199 | 0.002 | ||
| 1950 | #290 | 0.046 | #1036 | 0.002 | ||
| 1940 | #336 | 0.032 | #1053 | 0.003 | ||
| 1930 | #271 | 0.047 | #1170 | 0.003 | ||
| 1920 | #337 | 0.032 | #1210 | 0.003 | ||
| 1910 | #343 | 0.030 | #1100 | 0.004 | ||
| 1900 | #298 | 0.041 | #888 | 0.006 | ||
| 1890 | #241 | 0.055 | #665 | 0.008 | ||
| 1880 | #157 | 0.097 | #552 | 0.010 | ||
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