| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | over the [num ord] 20 years | 77 |
|
| 2 | over the [adj] 20 years | 53 |
|
| 3 | over the past 20 years | 52 |
|
| 4 | over the past 20 years | 52 |
|
| 5 | over the last 20 years | 39 |
|
| 6 | over the last 20 years | 39 |
|
| 7 | over the next 20 years | 38 |
|
| 8 | over the next 20 years | 38 |
|
