The Importance of Vault in Boom Beach
Now, let's see its real effect by an instance.
From the picture 1, we can see that when that guy as an invader to watch his opponent's island, the resources that he can plunder are 1750 gold and 5014 woods. But, from picture 2, we know the opponent' actual resources are 11421 gold and 12788 woods. See, the Vault's effect is obvious. Equally, as long as you upgrade your Vault to highest level, you can spare enough time for developing offensive forces.
“Protected resources = storage resource + (total resource - storage resource) * percentage of protection”.
Take my Vault for example, my Vault is level 10, can store 39000 woods and protect 63% of additional resources. Now, I have 90550 woods. So, when I was invaded, protected resources = 39000 + (90550 – 39000) * 63% = 71476.5. Then, the ratio of my actual losses: (90550 – 71476)/90550 = 21%.
Ultimately, thank Chuanqi89 for providing picture 1 and picture 2.