波卡（DOT）代幣經濟學

Polkadot's native token, DOT, is central to the network's security, governance, and resource allocation mechanisms. The token economics are designed to incentivize participation, secure the network through Nominated Proof-of-Stake (NPoS), and manage the allocation of shared resources (parachain slots/Coretime). As of April 14, 2024, the total token supply of DOT has increased to approximately 1.43 billion due to annual inflation, up from an initial supply of 1.00 billion.

Issuance Mechanism

Polkadot utilizes an inflationary model for DOT issuance, which is primarily used to fund staking rewards and the network treasury.

• Fixed Annual Issuance: The network transitioned from a percentage-based issuance rate to a fixed DOT issuance rate of 120 million DOT per year. This change, approved by a governance vote, makes DOT disinflationary over time as the fixed issuance becomes a smaller proportion of the overall network supply.
• Allocation of New DOT:
  • Approximately 100 million DOT of the annual issuance is designated for staking rewards.
  • The remainder funds the annual treasury budget.
• Variable Staking Rewards: Historically, the amount of new DOT directed toward stakers depended on the "ideal staking rate" versus the "system staking rate." When these rates were equal, all new DOT was rewarded to stakers. Tokens not distributed to stakers were allocated to the project's treasury. The ideal staking rate could vary between 45% to 75% based on the number of parachains that acquired a lease through an auction.

Allocation Mechanism

DOT is allocated across various functions, with staking and parachain bonding being the most significant mechanisms for locking up supply.

• Initial Supply: The initial total token supply was 1.00 billion DOT.
• Public Sale: A public sale distributed 224 million DOT (22.40% of the initial supply).
• Supply Distribution (Historical Example): A snapshot from mid-2022 showed the total supply of approximately 1.2 billion DOT distributed as follows:
  • Staking: 54% to 56%
  • Circulating: Stable, but a smaller portion
  • Other/Treasury: Smallest share
• Impact of Parachain Auctions: The introduction of parachain auctions significantly shifts the token distribution by locking up DOT for extended periods. Projections suggested that post-parachain launch, the distribution could change dramatically, with Parachain Bonds potentially accounting for 40% of the supply, Staking dropping to 40%, and Circulating supply reducing to 15%.
• Treasury Funding: The Polkadot treasury is funded by:
  • 100% of DOT transaction fees.
  • A variable portion of inflationary DOT rewards (when the system staking rate diverges from the ideal rate).
  • An undisclosed portion of validator-slashing penalties.
  • Direct contributions from tokenholders.

Usage and Incentive Mechanism

DOT serves as a utility token with multiple core functions that incentivize network security, governance, and resource allocation.

Network Security (NPoS)

Polkadot uses a Nominated Proof-of-Stake (NPoS) consensus mechanism, where DOT holders can participate as:

• Validators: Run nodes to verify parachain blocks and participate in consensus. Validators earn rewards based on "Era Points," which are determined by the amount of "payable actions" they perform during an era (24 hours), such as issuing validity statements or producing Relay Chain blocks. Rewards are distributed pro-rata based on these points, not solely on the amount staked.
• Nominators: Stake DOT to support validator candidates in return for rewards, minus any commission charged by the validator. Nominators risk not receiving rewards if their nominated validator is not elected or fails to accrue era points.

Governance

DOT holders have direct control over the network's evolution through an on-chain governance mechanism, OpenGov.

• Proposal Submission: Tokenholders can propose governance changes across 15 different "tracks," requiring a submission deposit of one DOT (which is refunded upon voting).
• Voting Power Multiplier: A user's voting weight can be increased by locking DOT for various lengths of time. The longer the lock, the higher the voting weight multiplier. For example, locking DOT for 32 periods (896 days) grants six votes per locked DOT.

Resource Allocation (Parachain Slots)

DOT is used to secure a parachain slot on the Relay Chain, Polkadot's central chain.

• Parachain Auctions: Potential parachains bid DOT in a candle auction to secure a slot lease. The DOT associated with the winning bid is locked for the duration of the lease.
• Crowdloans: Community members can contribute DOT to a parachain's bid through a crowdloan campaign, temporarily locking their DOT to help the project win a slot.
• Transaction Fees: DOT is used as the medium of exchange to pay network transaction fees.

Token Burn Mechanism

A deflationary mechanism exists within the Polkadot treasury: at the end of each spend period (24 days), 1% of the available funds in the treasury are burned.

Locking Mechanism and Unlocking Time

DOT tokens are locked in the network for two primary reasons: securing parachain slots and enhancing governance voting power.

Parachain Slot Bonding

• Locking Duration: DOT tokens bonded to secure a parachain slot are locked for the duration of the slot lease, which is typically 96 weeks.
• Unlocking: At the end of the slot lease, the locked DOT tokens are unlocked and returned to the bidders or crowdloan contributors.
• Crowdloan Impact: The unlocking of DOT from crowdloans can lead to significant temporary spikes in network activity, as observed in October 2023 when the first crowd loan batch unlocked, causing a sharp surge in active addresses.

Governance Locking

• Locking Duration: Tokenholders can voluntarily lock their DOT for various lengths of time (up to 32 periods or 896 days) to increase their voting weight.
• Unlocking: The DOT is unlocked after the specified lock-up period expires.

Staking

While staking involves bonding DOT to secure the network, the specific unbonding period was not detailed in the provided information. However, staking activity remains high, with the percentage of eligible supply staked fluctuating between 45% and 50% in early 2025.

The following table summarizes the key locking mechanisms and their associated durations: