Distribution of Staking Incentives

This applies to assets such as COMP for Compound and stkAave for Aave.

When a new expiry is created, a PendleYieldTokenHolder contract is also deployed alongside the OT and XYT contract. The PendleYieldTokenHolder will hold all the aTokens/cTokens. All the transfers of aToken/cToken is done from/to the PendleYieldTokenHolder

There will be COMP/StkAAVE rewards accrued in the PendleYieldTokenHolder Whenever there is new COMP/StkAAVE rewards coming into the PendleYieldTokenHolder, it will be distributed equally to the current OT holders:

• At time t0 : total amount of OT is $totalOT_0$ , a new user A mints $balanceA$ OTs
• At time t1 : There is $rewards_0$ coming in, A should get: $\cfrac{balanceA}{totalOT_0} \cdot rewards_0$
• At time t2 : There is $rewards_1$ coming in, A should get: $\cfrac{balanceA}{totalOT_1} \cdot rewards_1$

In total: A should get $balanceA \cdot \left(\cfrac{rewards_0}{totalOT_0} + \cfrac{rewards_1}{totalOT_1}\right)$

As such, we can generalise it and let:

$$L(t+1) = \cfrac{rewards_0}{totalOT_0} + \cfrac{rewards_1}{totalOT_1} + ... + \cfrac{rewards_t}{totalOT_t} = \sum_{i=0}^{t}\cfrac{rewards_i}{totalOT_i}$$

Then, rewards for a userA with balanceA for holding OT from t1 to t2 is: $balanceA \cdot (L(t2) - L(t1))$

As such, before any action that changes the totalOT, we will then need to:

• claim the COMP/StkAAVE rewards
• update L(t), based on the previous $totalOT$, and the amount of rewards that came in since the last L(t) update

Another note is that this way of accounting the rewards is exactly the same as how we account for the interests for a generic pool, especially when the "rewards/interests" do not grow by itself (same as a CompoundMarket, or CompoundLiquidityMining contract). Therefore, we try to keep the implementation to be as similar as possible, to reduce potential bugs and mistakes.