The ‘g-index’ was developed by Professor Leo Egghe in 2006 in response to the ‘h-index’. Both indices measure the output (quantity) and impact (quality or visibility) of an individual author. Egghe explains why he thinks the g-index is an improvement.
Egghe, Leo Prof.
"From h to g: the evolution of citation indicies,"
Research Trends: Vol. 1:
1, Article 5.
Available at: https://www.researchtrends.com/researchtrends/vol1/iss1/5