| year | know about, used |
Male | Female | AB | BSE |
| 1989 | n.a. | n.a. | n.a. | n.a. | n.a. |
| 1990 | 63% , 31% | 65% , 35% | 63% , 23% | 56% , 21% | 90% , 71% |
| 1991 | 79% , 43% | 76% , 44% | 82% , 40% | 74% , 33% | 94% , 72% |
| 1992 | 79% , 53% | 79% , 59% | 80% , 42% | 80% , 44% | 84% , 75% |
| 1993 | 79% , 71% | 79% , 79% | 79% , 61% | 80% , 67% | 90% , 76% |
| 1994 | 94% , 84% | 94% , 83% | 95% , 85% | 93% , 80% | 98% , 95% |
| 1995 | 91% , 91% | 90% , 90% | 92% , 92% | 90% , 90% | 92% , 92% |