At the peak of slavery, what fraction of landowners had slaves? 1/2? 1/4?
At the peak of slavery where? In the United States? In the 1860 census, the last one taken before the Civil War, there were 393,975 people who owned at least one slave. The total free population of the US was 27,233,198, and the total slave population was 3,950,546, for a total population of 31,183,744. So, about 1.3% of the US population were slaveholders, and about 12.7% of the population were slaves.
As for the percentage of landholders who owned slaves, that’s harder. According to the census data, there were 1,944,865 farms in the US., but I can’t find the other data I’d need.
I can also tell you that the state with the largest number of slaveholders in 1860 was Virginia, with 52,128 slaveholders, which was also the state with the largest number of slaves. The state with the highest percentage of slaves was South Carolina, where slaves made up 57.2% of the population.
Yes in the United States. And you can include pre-independence also if you can find the information.