Table 2.
General information of the time-series analysis.
| Variables | Total period (2008-2019) |
Period 1 (2008-2010) |
Period 2 (2011-2013) |
Period 3 (2014-2016) |
Period 4 (2017-2019) |
| Number of documents, n (%) | 5810 (100) | 308 (5.3) | 707 (12.2) | 1855 (31.9) | 2940 (50.6) |
| Number of words, n (%) | 25,556 (100) | 3814 (14.9) | 6868 (26.9) | 12,749 (49.9) | 16,831 (65.9) |
| Number of links in the word-document network, n (%) | 333,921 (100) | 14,724 (4.4) | 36,642 (11.0) | 107,405 (32.2) | 175,150 (52.5) |
| Number of links in the word-document network, TF-IDF (%) | 223,422 (100) | 10,643 (4.8) | 25,342 (11.3) | 72,230 (32.3) | 115,207 (51.6) |