Never had slavery been trans-Atlantic. This created a modern, globalized economy. Forced slavery in North America lead to major growth of industry back in Europe. Previously, Europeans had to use African slaves. During this time, there was no ‘unified’ African ethnicity. All of the various ethnicities fought each other, and they sold other Africans into slavery. Unlike past slavery, African slavery became purely racial. Slavery in Africa was often the product of conflict and war between tribes. Unlike in America, it was not based in race. Slaves were not able to travel freely in Africa, but they experienced greater freedom within the tribal compound than American slaves. Slaves in Africa were also not necessarily enslaved for life. Practices varied from tribe to tribe, blacks typically owned other blacks and often regarded their slaves as dependents. It was not unusual for slave owners to take their slaves into their family unit. Slavery status was inherited by the children of African slaves. A major factor was the domestic slave trade. This is where masters in Delaware, Maryland, Virginia, North Carolina, and Kentucky trimmed excess slaves from their workforces or switched entirely from slave labor to wage labor; they sold men, women, and children to slave traders. The traders in turn shipped these people to the slave markets of New Orleans and other cities for resale. The number of people traded was huge. Starting in the 1820s, about 150,000 slaves per decade moved toward the southwest either with their master or traders. Between 1820 and 1860, an estimated 50 percent of the slaves of the Upper South moved involuntarily into the Southwest.