Table 1.
The results of K-means cluster analysis in different time periods.
| Time Period | Clusters | States |
|---|---|---|
| The early phase (1 March–31 May) |
1 | NY |
| 2 | CA, IL, MA, MI, NJ, PA, TX | |
| 3 | The remaining states | |
| The middle phase (1 June–30 September) |
1 | CA, FL, TX |
| 2 | The remaining states | |
| The late phase (October–12 December) |
1 | CA |
| 2 | FL, IL, OH, TX | |
| 3 | AZ, CO, GA, IN, MI, MO, MN, NC, NJ, NY, PA, TN, WI | |
| 4 | The remaining states | |
| The whole period (1 March–12 December) |
1 | CA, FL, TX |
| 2 | AZ, CO, GA, IL, IN, MI, MN, MO, NC, NJ, NY, OH, TN, WI | |
| 3 | The remaining states |