What can cause the PPF to Shift Outwards? Can the PPF be Vertical or Horizontol?

-If the Amount, or Quality, of Resources Change for the Better -Increase in the Number of Workers, or more Natural Resources, or Better Technology or Labour Force, will lead to a PPF Outward Shift -This is because More Output is Produced using the Same Resources -And it can be Horizontal or Vertical, only if it affects Good X and not Good Y ie Better Quality Resources that concern Good X