FEE emissions schedule

FEE is emitted on an immutable schedule defined in FEEEmissionCurve.sol. The schedule is front-loaded but not a simple exponential decay: emissions ramp up to a peak at month 12, then taper for about three more years before the cap is reached.

Allocation

Total FEE supply cap: 63,000,000 FEE, split into two equal "sides":

• 31,500,000 FEE per side, emitted independently on the same curve.
• The two sides fund SP issuance (Stability Pool incentives via SpIssuance) and LP issuance (LP staking incentives via LpIssuance).

The two sides are independent — SP depositors and LP stakers each draw from their own 31.5M-FEE budget on the same time profile.

Shape

The schedule is encoded as 48 month-end cumulative checkpoints (months 0–47). Within each month emissions are linear; across months they form a smooth curve.

Key milestones, per side:

Month	Cumulative FEE	Monthly FEE	% of cap
1	681,103	681,103	2.2%
6	4,638,079	871,153	14.7%
12	10,869,621	1,170,447 (peak)	34.5%
18	17,255,215	982,399	54.8%
24	22,461,929	785,919	71.3%
36	29,338,722	392,959	93.1%
47	31,500,000	32,746	100%

After month 47 (= 4 × SECONDS_PER_YEAR from deployment, the HOT_END constant), getCumulativeIssued returns the cap. No further FEE is emitted from this contract.

Monthly emissions (per side)

Month  Monthly FEE
   1    681,103   ████████▓
   2    715,467   █████████
   3    751,563   █████████▌
   4    789,481   ██████████
   5    829,312   ██████████▌
   6    871,153   ███████████
   7    915,104   ███████████▌
   8    961,272   ████████████
   9  1,009,772   ████████████▌
  10  1,060,716   █████████████
  11  1,114,231   █████████████▌
  12  1,170,447   ██████████████  ← peak
  13  1,146,132   █████████████▌
  14  1,113,386   █████████████▌
  15  1,080,639   █████████████
  16  1,047,892   █████████████
  17  1,015,146   ████████████▌
  18    982,399   ████████████
  19    949,652   ███████████▌
  20    916,906   ███████████▌
  21    884,159   ███████████
  22    851,412   ██████████▌
  23    818,666   ██████████
  24    785,919   █████████▌
  25    753,173   █████████▌
  26    720,426   █████████
  27    687,679   ████████▌
  28    654,933   ████████
  29    622,186   ███████▌
  30    589,439   ███████▌
  31    556,693   ███████
  32    523,946   ██████▌
  33    491,200   ██████
  34    458,453   █████▌
  35    425,706   █████
  36    392,959   █████
  37    360,213   ████▌
  38    327,467   ████
  39    294,719   ███▌
  40    261,974   ███
  41    229,226   ██▌
  42    196,480   ██
  43    163,733   ██
  44    130,986   █▌
  45     98,240   █
  46     65,494   ▌
  47     32,746   ▎

Each █ represents roughly 83,500 FEE/month.

Why this shape

Three reasons, in priority order:

1. Front-loaded to bootstrap usage. The peak at month 12 (not month 1) gives initial depositors and LP stakers a chance to enter and accrue position before peak emissions hit. A pure-decay curve (highest at t=0) would over-reward whoever happens to be in the contract at the moment of deployment.
2. No long tail. The curve reaches the cap in 47 months, not asymptotically. Once the cap is hit, the SP and LP issuance contracts are functionally complete — there's no slow drip of fresh FEE indefinitely diluting holders.
3. Smooth and predictable. The schedule is purely a function of block.timestamp − deploymentTime. No governance vote, no rate changes, no admin pause. Anyone can compute their share of upcoming emissions exactly.

Comparison with Liquity V1

Liquity V1 issued LQTY on a 1-year half-life exponential decay (the standard (1 − 0.5^t) curve). That's extremely front-loaded: ~50% of all LQTY is emitted in year 1, ~75% by year 2, and the long tail asymptotically approaches the cap forever.

RAI Dollar's curve is also front-loaded, but in a different shape:

• It ramps up to peak emissions at month 12 instead of starting at peak.
• It terminates cleanly at month 47 instead of decaying forever.
• The total cap is reached in finite time, not asymptotically.

In practice, both produce roughly comparable cumulative-emitted-by-year curves for the first few years, but RAI Dollar's avoids the "first-block farmers get everything" pattern that exponential decay rewards.

Reading it on-chain

The library exposes two view functions used by SpIssuance and LpIssuance:

FEEEmissionCurve.getCumulativeIssued(uint256 elapsed) returns (uint256)
FEEEmissionCurve.getCumulativeFraction(uint256 elapsed) returns (uint256)

Both take seconds elapsed since deployment and return the cumulative-emitted FEE (and the fraction of cap, respectively). The integral over any window is simply the difference of two getCumulativeIssued calls.

Constants

SECONDS_PER_YEAR     = 31,536,000
MONTH_DURATION       = SECONDS_PER_YEAR / 12
HOT_END              = 4 × SECONDS_PER_YEAR   (4 years, schedule complete)
FEE_SUPPLY_CAP       = 31.5M × 1e18 (per side)

The full 48 month-end checkpoints are hardcoded as constants in FEEEmissionCurve._monthEndCumulative.