Price Stability Mechanisms (PSAMs)
One of the criticisms of emissions trading is price volatility. Carbon prices can swing dramatically in response to economic conditions, policy uncertainty, or market dynamics. Price Stability and Adjustment Mechanisms (PSAMs) are designed to smooth these swings while preserving the market's core function.
Why Price Stability Matters
Price volatility creates problems:
For investment decisions
If carbon prices might be €20 or €100 next year, how do you evaluate a low-carbon investment? Uncertainty paralyzes long-term planning.
For political sustainability
Price spikes can trigger political backlash. Price collapses can suggest the policy is not working.
For covered entities
Volatile costs are harder to manage than stable costs. Hedging is possible but adds expense.
For the market
Extreme volatility can reduce participation and liquidity as players exit or scale back.
Some volatility is natural and even useful. It reflects changing conditions. But excessive volatility, especially from temporary factors, can undermine the system's core purposes. PSAMs aim to reduce harmful volatility while preserving beneficial price signals.
The Menu of PSAMs
Several mechanisms are available, often used in combination:
Price floors
Minimum prices below which allowances will not be sold.
Price ceilings
Maximum prices above which additional supply is available.
Cost containment reserves
Additional allowances released at high prices.
Market stability reserves
Allowances withheld when surplus is high, released when prices are high.
Quantity adjustments
Automatic changes to auction volumes based on market conditions.
Price Floors
A price floor sets a minimum carbon price. If market prices would fall below this level, intervention prevents it.
How floors work:
Auction reserve prices: Allowances are not sold at auction below the floor price. If bids are all below the floor, allowances go unsold.
Floor taxes: If the allowance price falls below a set level, a tax tops it up to the floor.
Advantages:
- Provides minimum investment signal
- Revenue floor for government
- Prevents price collapse
Disadvantages:
- Reduces quantity certainty (unsold allowances)
- May conflict with pure cap-and-trade principles
- Requires setting the "right" floor level
California's auction reserve price:
California's cap-and-trade includes an auction reserve price that acts as a price floor:
| Year | Reserve price (USD/ton) |
|---|---|
| 2013 | $10.00 |
| 2015 | $12.10 |
| 2020 | $16.68 |
| 2024 | $22.21 |
| 2030 | ~$30 (projected) |
The reserve rises at 5% plus inflation annually. If auction prices fall to the reserve, allowances remain unsold. This has rarely happened because market prices have generally exceeded the reserve.
Price Ceilings
A price ceiling sets a maximum carbon price. If prices would rise above this level, additional supply is provided.
How ceilings work:
Unlimited supply at ceiling: Government sells unlimited allowances at the ceiling price. This effectively caps the price.
Cost containment reserves: A reserve of allowances is released at high prices, but supply is limited.
Advantages:
- Protects against price spikes
- Limits worst-case compliance costs
- Reduces political risk from price surges
Disadvantages:
- May compromise environmental integrity (more emissions if ceiling hit)
- Reduces quantity certainty
- May indicate cap was too tight
Not all price ceilings are created equal:
Hard ceiling (unlimited supply):
- Government commits to sell unlimited allowances at ceiling price
- Price absolutely cannot exceed ceiling
- Environmental outcome is not guaranteed
- Effectively becomes a carbon tax at the ceiling
Soft ceiling (limited reserve):
- Additional allowances available at ceiling, but supply is limited
- Price might temporarily exceed ceiling if reserve is exhausted
- Environmental integrity better protected
- Provides some cost containment without unlimited supply
Examples:
- California: Soft ceiling through price containment points (reserves of allowances at high prices)
- RGGI: Cost containment reserve provides limited additional allowances
The trade-off: A hard ceiling provides maximum cost certainty but sacrifices quantity certainty. A soft ceiling provides some cost protection while maintaining more environmental integrity.
The Price Collar
A price collar combines floor and ceiling:
How it works:
- Set a floor (minimum price)
- Set a ceiling (maximum price)
- Prices fluctuate freely between them
- Intervention only at the boundaries
Advantages:
- Contains price within a known range
- Preserves market function within the band
- Balances cost certainty and quantity certainty
Disadvantages:
- Narrow collars may be too restrictive
- Wide collars may not provide meaningful stability
- Setting both boundaries is challenging
A price collar works like guardrails on a highway. The road (prices) can curve freely within the lane. Only if you hit the guardrail (floor or ceiling) does intervention occur. Most of the time, you stay within the lane.
Quantity-Based Mechanisms
Instead of targeting prices directly, some mechanisms adjust allowance quantities:
Market Stability Reserve (MSR)
When surplus allowances exceed a threshold, allowances are withheld from auctions and placed in a reserve. When surplus is low, allowances are released from the reserve.
Automatic cap adjustment
The cap itself adjusts based on market conditions or price signals.
Dynamic allocation adjustments
Free allocation changes based on activity levels or prices.
| Mechanism | Targets | Preserves quantity certainty? | Preserves price stability? |
|---|---|---|---|
| Price floor | Price | Partially | Yes |
| Price ceiling | Price | No (if hit) | Yes |
| Quantity reserve | Both | Yes | Partially |
Choosing the Right Mechanism
The best PSAM depends on priorities:
If environmental integrity is paramount:
Use quantity-based mechanisms like the MSR. The cap remains fixed; prices adjust.
If cost certainty is paramount:
Use price collars or hard ceilings. Costs are bounded; quantity adjusts.
If political feasibility is key:
Use mechanisms that prevent both price spikes and collapses. Both extremes create political problems.
If simplicity is valued:
A price floor (auction reserve) is simpler than complex reserve mechanisms.
Criticisms of PSAMs
Some argue PSAMs undermine the ETS concept:
"It's not real cap-and-trade"
If prices, not quantities, are what's controlled, you have effectively created a carbon tax with extra steps.
"Markets should clear"
Intervention distorts price signals. Let markets find their level.
"Complexity increases"
Each PSAM adds rules, exceptions, and administrative burden.
"Gaming opportunities"
Sophisticated players may exploit PSAM triggers.
The Counter-Arguments
Despite criticisms, PSAMs are now mainstream:
Pragmatism
Pure cap-and-trade with extreme volatility may not survive politically.
Investment signals
A stable price signal, even if somewhat artificial, may be better for investment than a volatile pure market price.
Learning
As systems gain experience, PSAM calibration improves.
Almost all major ETS systems now include some form of PSAM. The debate has shifted from "whether" to "how" to implement price stability mechanisms while preserving market benefits.
Looking Ahead
The next lesson examines two specific PSAMs in more detail: price floors and ceilings. We will see how different jurisdictions have implemented these mechanisms and what they have learned.