The social sciences (e.g. economics, geography, psychology) have over the past decades shown a rapid transition from traditionally qualitative research methods to quantitative analysis techniques. This 'quantitative revolution' comprises of various statistical methods, such as regression analysis, multivariate statistical analysis, logistic regression, principal component analysis, and so forth. All these methods serve to 'measure the unmeasurable' (Nijkamp, 1985), and are also increasingly employed in the spatial sciences (geography, regional science, transportation science, ecology, political science etc.