In the 1980s Bono had a lustrous mane of often mulletted hair, as was then the fashion.
Sometime in the 90s it started receding a bit, and diffuse thinning too.
Hairloss of this type can be covered up quite well with a concealer such as Toppik or DermMatch.
He seems to have been a regular user of black hair dye too, which can accentuate hairloss when the natural coloured roots grow through.
As one of the most famous people in the world, it has been interesting to see Bono's reaction to his hairloss.
Rather than embrace it, it appears he felt it necessary to cover it up, which he has done with reasonable success up to now.
In an interview for Q magazine back in 2002, Chris Martin of Coldplay claimed that Bono had a hair transplant.
It doesn't look like he'll be able to cover up his hairloss for much longer unless he employs a hair piece of some sort.
Bono's hair is the subject of much discussion on U2 internet forums, and there is a Facebook group and website dedicated to his baldness.
Norwood Rating : difficult, but I'd go for a diffuse 3