| Value | Category | Cases | |
|---|---|---|---|
| 1 | No, no difficulty | 14070 |
97.7%
|
| 2 | Yes, some difficulty | 292 |
2%
|
| 3 | Yes, a lot of difficulty | 30 |
0.2%
|
| 4 | Yes, cannot see at all | 9 |
0.1%
|
| Sysmiss | 1891 |