Some people have suggested that the 20% interest rate for the first year is too high. It sounds like a lot, but not all of that will be realized. I will attempt to estimate an upper limit for the inflation percentage and compare it to Bitcoin and Litecoin.
First of all, mining ended before the 20 billion coin mark (I suspect this was due to POS blocks eating up potential POW blocks). The last POW block was somewhere around #100800, and there were only 18.6 billion coins at that time. Therefore, the number of coins available for the 20% POS reward is less than expected.
Secondly, not all of those 18.6 billion coins will produce new POS coins. Transactions destroy coin days, and the percentage of coin days destroyed in each block is currently around 60%:
http://mintcoin-explorer.info/block/a562045650e17ae6b1a3029ce93b1483bc116427fcaf7495fb62696165918bdeOf course, some of this could be people transferring coins the day after they receive a POS reward (I also don't know if this number includes coin days destroyed by minting). Let's suppose that the relevant coin day destruction is closer to 20% (remember I'm looking for an upper limit on coin supply). In other words I'm estimating that fewer than 80% of coins stored in wallets will be staked for a whole year rather than spent or transferred.
Thirdly, some of those initial 18.6 billion coins are stored on exchanges. From earlier investigations in this forum (thanks rmoraos), it looks like the exchanges are not collecting POS rewards on the coins that they hold. I checked earlier today, and there were a total of 1 billion Mintcoins for sale on the order books at Mintpal and Cryptsy. That means that
at most 17.6 billion of the initial POW coins are stored in wallets.
My upper limit for the number of coins collecting compound interest since the end of POW is 14 billion (80% of the 17.6 billion coins stored in wallets). 20% interest on 14 billion coins compounded every 20 days for a year works out to about 3.1 billion new coins. Therefore, there will be fewer than 21.7 billion Mintcoins in existence by March 9, 2015. With the decreasing interest rate, it will take a while to reach 70 billion coins.
Summary:
Increase in the number of coins over the next year:
Mintcoin: 16.6% (at most)
Bitcoin: 10.4% (12,560,000 coins, 1,312,500 mined in a year)
Litecoin: 39.1% (26,890,000 coins, 10,518,980 mined in a year)
agree, but
18.6 billion in 5 weeks - 3.72 billion in one week - price 10 satoshi
20% of 18.6 billion in 52 weeks(first year) - 18.6*20%/52 weeks = 0.071 billion in one week - price 3.72/0.071*10 satoshi = 520 satoshi
so, true price 520 satoshi