I'm with BillO. Some info from the attached text and tables:
--A sophisticated demographic analysis by Daniel Scott Smith that
relied on an analysis of published aggregate data and a preliminary version of the 1860 IPUMS sample also indicated equal participation by nativity.
--The 1860 population is estimated by weighting the IPUMS samples with the PERWGT variable, cross
‐
tabulating by age group and birth region, and adjusting the resulting counts for census undercount using the weighted average age 10 ‐ 44 sectional estimates in Hacker (forthcoming).
Say whaaaaaaat?
This reads more like a masters' thesis or doctoral dissertation than an article for Civil War History magazine.