434 Glossary
better off without making any of the others worse off is called a Pareto
improvement. If economic allocation in any system is not Pareto ef-
cient, there is a theoretical potential for a Pareto improvement, that
is, an increase in Pareto efciency. An allocation is called (strongly)
Pareto optimal when no further Pareto improvements can be made.
Pascal (Pa): The SI unit of pressure: 1 Pa ≡ 1 N/m
2
, 1 kPa = 0.14504 psi,
1MPa= 145 psi.
Path (in graph theory): A route that does not pass any node (vertex) more
than once. If the path does not pass any node more than once, it is a
simple path. See also walk.
Parity (in economics): When the cost of a good or service equals the cost of a
competing good or service. Grid parity ...