Recently, sharp eyed miners discovered that per block mining reward has been decreased from 11.41553 down to 11.09852. What is the reason for that?

It is because of the NKN economic model, that 300 million NKN tokens will be mined over 25 years, but with decreasing rewards. The formula is like this:

Annual NKN mining reward is 18.5-0.5T in millions, where T is the year of mining since mainnet launch and T is between 1 and 25. It is depicted in the following chart:

The blocks generated per year is constant at about 15,768,000 blocks given 20s block interval (`60*60*24*365/20`

). Therefore, the total mining reward in each year is:

- 1st year (block 1 - 15,768,000): 18,000,000
- 2nd year (block 15,768,001 - 31,536,000): 17,500,00
- …
- 25th year (block 378,432,001 - 394,200,000): 6,000,000

And per block reward will be:

- 1st year: 11.41553 (18,000,000/15,768,000)
- 2nd year: 11.09842 (17,500,000/15,768,000)
- and so forth
- 25th year: 3.80518 (6,000,000/15,768,000)

It is a bit like Bitcoin mining, that it rewards early participants of the mining community. Different from Bitcoin though, the decreasing in mining reward is linear over 25 years instead of halving every four years.