Upvote:2
I may note that in the 1850 census the number of blacks was listed as 3,233,057 and in the 1860 census it was 3,853,478, an increase of 620,241 or 19.18 %, while the number of mulattoes was 405,751 in 1850 and 588,352 in 1860, an increase of 182,601 or 45.00 %.
Population of the United States in 1860; Compiled from the Original Returns of the Eighth Census, under the direction of the secretary of the Interior, by Joseph C. G. Kennedy 1864. Introduction, page x.
https://archive.org/details/populationofusin00kennrich/page/n31
And the colored population of the United states - combined blacks and mulattoes - is listed as 757,208 in 1790, 1,002,067 in 1800 (increase of 244,859 or 32.33 %), 1,377,808 in 1810 (increase of 375,741 or 37.49 %), 1,771,656 in 1820 (increase of 393,848 or 28.58 %), 2,338,642 in 1830 (increase of 566,986 or 32.00 %), 2,873,648 in 1840 (increase of 535,006 or 22.87 %), 3,638,808 in 1850 (increase of 765,160 or 26.62 %), 4,441,830 in 1860 (increase of 803,022 or 22.06 %), and 4,880,009 in 1870 (increase of 438,179 or 9.86 %).
Compendium of the 9th Census pages 12 and 13.
https://www2.census.gov/library/publications/decennial/1870/compendium/1870e-02.pdf?#2
And those figures may help to indicate the possible size and scope of any possible excess mortality among black Americans during the decade of 1860 to 1870.