Answer:
an increase in the unemployment rate.
Step-by-step explanation:
Production possibility curve shows the output of two products that can be achieved with a given level of resources.
In all other instances given above (new source of renewable energy, improved production technology, and increase in quality of labor force), there is increase in resources that will generally result in increase in production.
However increased unemployment results in reduced resources and reduction in production level (will shift production possibility curve to the left).