Category	2018	2015		2013	2010	2007
Don't know	0	1		0	1	1
I have never heard of it (%)	29	38		26	33	35
I've heard of it but I do not know what it is (%)	30	30		30	28	30
I've heard of it and I know what it is (%)	41	31		44	38	35