Without recognising indivisibilities — in human person, in residences, plants, equipment, and in transportation — location patterns, down to those of… - Tjalling Koopmans

We look upon economic theory as a sequence of conceptual models that seek to express in simplified form different aspects of an always more complicated reality.

While it was long possible and sometimes tempting for physicists to deny the usefulness of the molecular hypothesis, we economists have the good luck of being some of the ‘molecules’ of economic life ourselves, and of having the possibility through human contacts to study the behavior of other ‘molecules’.

Econometrics may be defined as the quantitative analysis of actual economic phenomena based on the concurrent development of theory and observation, related by appropriate methods of inference.