The overall number of the clusters for the 5-year sub-periods varies between three and eight with the cosine distance method resulting as the optimum for five sub-periods and the correlation distance method optimum for three sub-periods (Table 5).
Number of clusters identified for each 5-year sub-period
| No. . | Period . | Number of clusters . | Distance method . |
|---|---|---|---|
| 1 | 1980–1984 | 3 | Cosine distance |
| 2 | 1985–1989 | 5 | Correlation distance |
| 3 | 1990–1994 | 8 | Cosine distance |
| 4 | 1995–1999 | 5 | Cosine distance |
| 5 | 2000–2004 | 7 | Cosine distance |
| 6 | 2005–2009 | 5 | Cosine distance |
| 7 | 2010–2014 | 5 | Correlation distance |
| 8 | 2015–2020 | 4 | Correlation distance |
| No. . | Period . | Number of clusters . | Distance method . |
|---|---|---|---|
| 1 | 1980–1984 | 3 | Cosine distance |
| 2 | 1985–1989 | 5 | Correlation distance |
| 3 | 1990–1994 | 8 | Cosine distance |
| 4 | 1995–1999 | 5 | Cosine distance |
| 5 | 2000–2004 | 7 | Cosine distance |
| 6 | 2005–2009 | 5 | Cosine distance |
| 7 | 2010–2014 | 5 | Correlation distance |
| 8 | 2015–2020 | 4 | Correlation distance |