Why was the Sahara also called the Trans-Sahara Trade Route?

Trans-Saharan trade requires travel across the Sahara between sub-Saharan Africa and North Africa. While existing from prehistoric times, the peak of trade extended from the 8th century until the early 17th century. ... Cattle were introduced to the Central Sahara (Ahaggar) from 4000 to 3500 BC.

1920 census

the census was scheduled for january the 1st, as the government believed that more farmers would be in their homes by that time instead of april. the census did not ask about unemployment, the number of children, and how long was a couple married were not taken into consideration. individuals were considered as residents of the places they normally slept, not the places were they worked at or visited.

2010 census

the census was scheduled for april 1st, 2010. it was the shortest census in history: it only contained 10 questions related to name, age, gender, ethnicity, relationship, and whether the citizen owned a home or rented one. the government launched a website in order to provide the citizens with information regarding the census. there were also "teach census weeks" in schools nationwide.