| Value | Category | Cases | |
|---|---|---|---|
| 1 | No difficulty | 2592618 |
96.1%
|
| 2 | Yes, some difficulty | 90384 |
3.3%
|
| 3 | Yes, a lot of difficulty | 12289 |
0.5%
|
| 4 | Cannot see at all | 3507 |
0.1%
|
| Sysmiss | 384774 |