Study the data tables below which show the changing population structure of Wales.
| Age (years) | Number of people |
|---|---|
| 0-19 | 780,000 |
| 20-39 | 750,000 |
| 40-59 | 690,000 |
| 60-79 | 530,000 |
| 80+ | 110,000 |
| Age (years) | Number of people |
|---|---|
| 0-19 | 690,000 |
| 20-39 | 770,000 |
| 40-59 | 810,000 |
| 60-79 | 680,000 |
| 80+ | 170,000 |
Which age group experienced a decrease in the number of people between 1991 and 2021?