Evolutionary Biological Data Science Laboratory

impact vitality

Impact Vitality (Rons and Amez 2008, 2009) is similar in concept to the trend h-index, but more complicated to measure. If c^x is the total number of citations (across all publications) from year x, and w is the number of years back from the present (year Y) one wishes to calculate the metric for (the citation window), then

$$IV\left(w\right)=\frac{w\left(\frac{\sum\limits_{i=1}^{w}{\frac{c^{Y-w}}{i}}}{\sum\limits_{i=1}^{w}{c^{Y-w}}} \right)-1 }{\left(\sum\limits_{i=1}^{w}{\frac{1}{i} } \right)-1}.$$

The numerator of the numerator is the sum of citation counts divided by their age for the window of time in question; the denominator of the numerator is the total number of citations for the same window of time. An impact vitality score of 1 indicates that the number of citations is approximately constant over time. A value above 1 indicates that the number of citations is increasing through time, while a value below 1 indicates the number of citations is decreasing through time. Individuals with very different total numbers of citations can have identical scores because the metric is focused on proportional change and not absolute numbers. However, even beyond the issues of more difficult data collection, this metric has odd properties because of its overwhelming focus on immediacy. It would produce a higher score for someone with just 1 citation a year ago and no citations 2 years ago than another person with 1,000 citations 2 years ago and no citations one year ago.

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