Without food people became malnourished therefore a decrease of population due to famine so no births and productivity since people were too weak to work.
I believe its the oil crisis of 1973.
The answer is concrete.
<span>The Romans' ingenious use of concrete was
instrumental in the construction of the great cathedrals of Europe 1,000 years
later. Vaulting of concrete completed the building of the great cathedrals and amphitheater
of the Romans. It also made the Pantheon dome and the Palestrina’s Sanctuary of
Fortuna Primigenia. </span>
