user247: 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?

user88: As explained in the docs, rewards come from:

Transaction fees (increases in time if adoption and network traffic increases)
Monetary expansion (decreases in time)

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.


247: <p>I remember that initially the percentage of rewards for delegators was around 5.12% visiting <a href="https://cardano.org/calculator/?calculator=delegator" rel="noreferrer">Cardano Calculator</a>. Now they are approximately 4.6083%.</p>
<p>How this is calculated?
Will the percentage decrease over the years?</p>
 88: <p>As explained in the <a href="https://docs.cardano.org/en/latest/explore-cardano/understanding-pledging-and-rewards.html#distributing-rewards" rel="noreferrer">docs</a>, rewards come from:</p>
<ul>
<li>Transaction fees (increases in time if adoption and network traffic increases)</li>
<li>Monetary expansion (decreases in time)</li>
</ul>
<p>The sum of these is denoted by <code>R</code> and the share of rewards that a given pool gets is given by:</p>
<blockquote>
<p><a href="https://i.stack.imgur.com/QwqEx.png" rel="noreferrer"><img src="https://i.stack.imgur.com/QwqEx.png" alt="enter image description here" /></a></p>
<p>where: R - total available rewards for this epoch</p>
<p>a0 - pledge influence factor (can be between 0 and infinity)</p>
<p>z0 - relative pool saturation size, i.e. 0.5% based on a number of
desired pools (k=200)</p>
<p>σ - stake delegated to the pool (including stake pledged by the owners
and stake delegated by others)</p>
<p>σ’ = min(σ, z0) - as σ, but capped at z0</p>
<p>s - stake pledged by the owners</p>
<p>s’ = min(s, z0) - as s, but capped at z0</p>
</blockquote>
<p>About monetary expansion and issuance, you may check <a href="https://docs.cardano.org/en/latest/explore-cardano/cardano-monetary-policy.html" rel="noreferrer">this section of the docs</a>.
Essentially, every epoch, a fixed fraction <code>ρ</code> is taken from the ADA reserves and is added into <code>R</code>. From the docs:</p>
<blockquote>
<p>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.</p>
</blockquote>
