Engineers, who were the leaders of the Underground Railroad, helped slaves who were running away by providing them with food, shelter, and sometimes jobs. They hid the slaves from people who were trying to catch them and return them to slavery.
The GDP per Capita, in Nigeria, when adjusted by Purchasing Power Parity is equivalent to 32 percent of the world's average.
GDP is the measure of output produced within a country's borders. Imagine an economy that just produces shoes. Nominal GDP is affected by the price level. If prices increase, even though the number of shoes produced hasn't changed, nominal GDP increases. A more correct measure would be real GDP which is GDP corrected for price increases.