I remember that initially the percentage of rewards for delegators was around 5.12% visiting Cardano Calculator. Now they are approximately 4.6083%.
How this is calculated? Will the percentage decrease over the years?
As explained in the docs, rewards come from:
The sum of these is denoted by
R and the share of rewards that a given pool gets is given by:
where: R - total available rewards for this epoch
a0 - pledge influence factor (can be between 0 and infinity)
z0 - relative pool saturation size, i.e. 0.5% based on a number of desired pools (k=200)
σ - stake delegated to the pool (including stake pledged by the owners and stake delegated by others)
σ’ = min(σ, z0) - as σ, but capped at z0
s - stake pledged by the owners
s’ = min(s, z0) - as s, but capped at z0
About monetary expansion and issuance, you may check this section of the docs.
Essentially, every epoch, a fixed fraction
ρ is taken from the ADA reserves and is added into
R. From the docs:
Calculating the ‘reserve half life’ (that is, the time that it takes for half of the reserve to be used up) visualizes the impact of choosing a specific value of ρ over another. This was the subject of much discussion, and eventually, the value assigned was 0.3%. The reason why is that mathematical projections showed that a ρ (the fixed percentage of ada going into the virtual pot every epoch) value of 0.3% would mean a reserve half-life of four to five years. In simple terms, just half of the remaining reserve would be used every four to five years.