To calculate the mining yield you must know a few bits of information. These numbers are based on current conditions:

Get koin.total_supply at https://koinosblocks.com/address/15DJN4a8SgrbGhhGksSBASiSYjGnMU8dGL and click on total_supply and READ and dividing by 10^8. In this case we have 10,589,924.64498886 KOIN.

Get vhp.total_supply at https://koinosblocks.com/address/1AdzuXSpC6K9qtXdCBgD5NUpDNwHjMgrc9 and click on total_supply and READ then dividing by 10^8. In this case, we have 7,963,448.62694314 VHP.

Calculate the total blocks per year.
365 days/year x 24 hours/day x 60 minutes/hour x 60 seconds/minute and divide that by 3 second block time. This equates to 10,512,000 blocks/year. 
Calculate the total reward available by multiplying the inflation rate (2%) and the vSupply. 18,553,373.271932 x 0.02 = 371,067.46543864 KOIN

Calculate the yield by dividing the reward pool size by the vhp.total_supply.
371,067.46543864 KOIN / 7,963,448.62694314 VHP x 100 = 4.6596328 %
WARNING! This number assumes that ALL VHP burned is actively producing. But this might not be the case if someone burns KOIN to receive VHP and does not use the VHP in block production. This would be the case with VHP that sits on an exchange to act as liquidity, or someone who simply stoped running their mining node.
You can also determine other useful bits of information:
The Per Block Reward in KOIN can be determined by dividing the reward pool size by the blocks per a year 371,067.46543864/10,512,000 = 0.035299416 KOIN per block.
The most important thing to remember here is that you must know the total supply of KOIN and VHP separately to perform these calculations.