First, the number of periodicals included in the natural index is too small. At present, Nature Index only counts 82 periodicals, covering only a few disciplines such as life science, physics, chemistry, earth and environmental science. Such a small capacity and narrow field are not enough to comprehensively and objectively reflect the published articles of institutions/universities.
Second, not all the periodical papers included in the natural index are high-level academic achievements. Take the top nature as an example. It has been a popular science publication since its publication. There is no denying the greatness of nature, but the articles published in Nature cannot be simply equated with high-level scientific research achievements.
At the same time, even a high-level academic journal does not mean that every paper above is a high-level academic achievement. A typical proof is that papers from high-level journals are often rejected.
Third, the calculation method of natural index can't stand scrutiny. Natural index uses two methods to calculate the output of a paper: one is the number of papers (AC). No matter whether there are one or more authors in a paper, each author's country or institution gets an AC score of 1.
The other is fractional measurement (FC). The total FC score of a paper is at most 1, which means that each author's contribution is the same, and all authors share the FC score of 1 equally.
It is not difficult to find that the "value" of the first AC calculation method will be improved because of the increase of signers; The second FC calculation method does not consider the contribution of collaborators to the paper. Undoubtedly, these two calculation methods are obviously "disregarding the facts".
To sum up, the so-called natural index, to put it bluntly, is a summary of papers published by various institutions/universities in 82 designated journals within one year, and the statistical processing is relatively rough. Therefore, it cannot reflect the scientific research strength of global scientific research institutions and universities, nor can it represent the global academic ranking. We can't take it too seriously.