“Have you been happier in slavery or free?” a young Works Project Administration interviewer in 1937 asked Lorenzo Ivy, a former slave, in Danville, Va. Ivy responded with a memory of seeing chained African-Americans marching farther South to be sold.

“Truly, son, the half has never been told,” he said.

This anecdote is how Edward E. Baptist opens “The Half Has Never Been Told: Slavery and the Making of American Capitalism,” an examination of both the economic innovations that grew out of the ever-shifting institution of slavery and the suffering of generations of people who were bought and sold.

Mr. Baptist, a history professor at Cornell, said in an interview that his book represented his decade-long effort to blend these two aspects. Published in September, “The Half” joins a new wave of scholarship about the centrality of slavery — and the cotton picked by slaves — to the country’s economic development.

Mr. Baptist shows the ways that new financial products, bonds that used enslaved people as collateral and were sold to bondholders in this country and abroad, enriched investors worldwide. He also emphasizes viciously enforced slave labor and migration. The cotton boom led planters to sell slaves — one million moved from old to new slave states from the 1790s to the 1860s. Productivity, he argues, came through punishment. Enslaved and formerly enslaved people like Ivy are at the center of this sprawling story.