So I opened 3 tins yesterday:
1. tin: 1 shiny (Xurkitree), 1 FA (Birds)
2. tin: 1 shiny (Frogadier), 1 FA (Jessie & James)
3. tin: 2 shinies (Gardevoir GX and Eevee), 1 FA (Birds), 1 holo (Jessie & James).
So if you have a lot of tins like my 3rd one, you would say it's 50 %, if you have a lot...