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).

Table 5

Number of clusters identified for each 5-year sub-period

No.PeriodNumber of clustersDistance method
1980–1984 Cosine distance
1985–1989 Correlation distance
1990–1994 Cosine distance
1995–1999 Cosine distance
2000–2004 Cosine distance
2005–2009 Cosine distance
2010–2014 Correlation distance
2015–2020 Correlation distance
No.PeriodNumber of clustersDistance method
1980–1984 Cosine distance
1985–1989 Correlation distance
1990–1994 Cosine distance
1995–1999 Cosine distance
2000–2004 Cosine distance
2005–2009 Cosine distance
2010–2014 Correlation distance
2015–2020 Correlation distance

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