Okay Let's ponder on this,In 1980 Nigeria Exchange 80kobo to $1,But today Nigeria exchanges #480 to $1
But Here are my Reasons,we shouldn't be surprised,we  were far more productive in1980 than we are today.
In 1980s the key reasons for economic growth were as follows
(1) Nigeria was a net exporter of refined petroleum products. Today  they import all their petroleum products.
(2) They rode in locally assembled cars,buses and trucks.peugeot cars in kaduna and Volkswagen cars in Lagos.
(3)Stauyr at bauchi producing our Agricultural tractors and it was not just assembly,we were producing many of the components
(4)Tyres produced by Dunlop in Lagos and mitchelin in portharcourt. And I mean Tyres produced from rubber plantations located in ogun and rivers state
(5) We were using refrigerators, freezer and Air conditioners produced by thermocool and Debo
(6)we were putting on clothes produced from the UNTL textile Milly in Kaduna and chellarams in Lagos,Not from imported cotton but from cotton grown in Nigeria.