Stability Pool and Liquidations

What is the Stability Pool?

The Stability Pool is the first line of defense in maintaining system solvency. It achieves that by acting as the source of liquidity to repay debt from liquidated Troves—ensuring that the total PUSD supply always remains backed.

When any Trove is liquidated, an amount of PUSD corresponding to the remaining debt of the Trove is burned from the Stability Pool’s balance to repay its debt. In exchange, the entire collateral from the Trove is transferred to the Stability Pool.

The Stability Pool is funded by users transferring PUSD into it (called Stability Providers). Over time Stability Providers lose a pro-rata share of their PUSD deposits, while gaining a pro-rata share of the liquidated collateral. However, because Troves are likely to be liquidated at just below 110% collateral ratios, it is expected that Stability Providers will receive a greater dollar-value of collateral relative to the debt they pay off.

Why should I deposit PUSD to the Stability Pool?

Stability Providers will make liquidation gains (see below) and receive early adopter rewards in form of PYQ tokens.

What are liquidations?

To ensure that the entire stablecoin supply remains fully backed by collateral, Troves that fall under the minimum collateral ratio of 110% will be closed (liquidated).

The debt of the Trove is canceled and absorbed by the Stability Pool and its collateral distributed among Stability Providers.

The owner of the Trove still keeps the full amount of PUSD borrowed but loses ~10% value overall hence it is critical to always keep the ratio above 110%, ideally above 150%.

Who can liquidate Troves?

Anybody can liquidate a Trove as soon as it drops below the Minimum Collateral Ratio of 110%. The initiator receives a gas compensation (10 PUSD + 0.5% of the Trove's collateral) as reward for this service.

How am I compensated for liquidating a Trove?

The liquidation of Troves is connected with certain gas costs which the initiator has to cover. The cost per Trove was reduced by implementing batch liquidations of up to 95 Troves but with the aim of ensuring that liquidations remain profitable even in times of soaring gas prices the protocol offers a gas compensation given by the following formula:

gas compensation = 10 PUSD + 0.5% of Trove's collateral (Matic)

The 10 PUSD is funded by a Liquidation Reserve while the variable 0.5% part (in Matic) comes from the liquidated collateral, slightly reducing the liquidation gain for Stability Providers.

How do I benefit as a Stability Provider from liquidations?

As liquidations happen just below a collateral ratio of 110%, you will most likely experience a net gain whenever a Trove is liquidated.

How do I benefit as a Stability Provider from early adopter rewards?

First you need to open a Trove, borrow PUSD, and deposit it to the Stability Pool. After making your deposit, you will start accumulating a reward (in PYQ) proportional to the size of your deposit on a continuous basis. The reward is calculated according to the rewards schedule and the kickback rate of the front end that you used for making the deposit. Rewards will be the highest for early adopters of the system.

At any point in time, you can withdraw your pending rewards to your Matic address.

Can I withdraw my deposit whenever I want?

As a general rule, you can withdraw the deposit made to the Stability Pool at any time. There is no minimum lockup duration. However, withdrawals are temporarily suspended whenever there are liquidatable Troves with a collateral ratio below 110% that have not been liquidated yet.

Can I lose money by depositing funds to the Stability Pool?

While liquidations will occur at a collateral ratio well above 100% most of the time, it is theoretically possible that a Trove gets liquidated below 100% in a flash crash or due to an oracle failure. In such a case, you may experience a loss since the collateral gain will be smaller than the reduction of your deposit.

If PUSD is trading above $1, liquidations may become unprofitable for Stability Providers even at collateral ratios higher than 100%. However, this loss is hypothetical since PUSD is expected to return to the peg, so the “loss” only materializes if you had withdrawn your deposit and sold the PUSD at a price above $1.

Please note that although the system is diligently audited, a hack or a bug that results in losses for the users can never be fully excluded.

What happens if the Stability Pool is empty when liquidations occur?

If the Stability Pool is empty, the system uses a secondary liquidation mechanism called redistribution. In such a case, the system redistributes the debt and collateral from liquidated Troves to all other existing Troves. The redistribution of debt and collateral is done in proportion to the recipient Trove's collateral amount.