Across the various editions of the WJ Tests of Cognitive Abilities (WJ, WJ-R, WJ III, WJ IV), the authors continually have sought to improve the measurement of intelligence via following contemporary research and theory. As a result, in contrast to many other IQ tests, the WJ has been known for global IQ scores (original called Broad Cognitive Ability, later changed to General Intellectual Ability) that changed rather dramatically from one revision to the next. We the WJ authors might be considered to be the Elon Musk of IQ test development.
I was recently asked to explain the changing nature of the BAC/GIA scores. The result is the table inserted below (double click to enlarge). I believe the table is self-explanatory. A nice PDF copy can be downloaded here. Enjoy.