Blackcoin has 0.97% yearly inflation. Which currently results in about 5% dividends. It doesn't punish people who don't stake, it means it can be freely used and traded without seeing your capital depreciate. Yet the staking reward is strong enough to be a very attractive coin to hold and speculate long term on.
The thing to take away here is that protocol means something. Every parameter needs to be taken seriously and Blackcoin has them all balanced out properly.
In a more mature and rational market you may also have to take into account the Relative Purchasing Power Parity for the inflation rates of competing currencies like the USD or Bitcoin.
So, if all else remains the same in a market (no userbase growth for example), Blackcoin might be expected to appreciate vs the USD by 2% and depreciate against Bitcoin by 1% (after it reaches 0% inflation).
Real returns would be 4% with 5% interest and 1% inflation if looking at Blackcoin in isolation. But when comparing to the USD would be 7.1% gain per year, taking into account USD inflation of 3%. It would only be 3.95% gain vs Bitcoin.
We're years away from the market reaching maturity though.