The Averch–Johnson (A–J) effect is the prediction that a firm regulated under rate-of-return regulation may use too much capital relative to labor (an inefficiently high capital-labor ratio), even when that input mix is not cost-minimizing.
The core mechanism
In a competitive setting, a firm that produces a given output chooses inputs to minimize cost. For a production function (q=f(K,L)) with input prices (r) (capital) and (w) (labor), the cost-minimizing condition can be expressed as:
[ \text{MRTS}_{KL} = \frac{w}{r}. ]
Under rate-of-return regulation, prices are set so that the firm is allowed to earn an “acceptable” return (\bar r) on a regulated capital base (the rate base). If (\bar r) is above the true cost of capital (or if the regulatory formula rewards a larger capital base), then adding capital can increase allowed earnings.
Economically, this can make capital look artificially “cheap” from the firm’s perspective, tilting choices toward capital-intensive techniques. The result is overcapitalization (sometimes called “gold-plating”).
When the A–J effect is more likely
The distortion is typically discussed in settings like regulated utilities, and is more plausible when:
- the allowed return (\bar r) exceeds the true cost of capital,
- the regulatory rule ties allowed revenue closely to the measured capital base,
- capital expenditures are easier to justify or pass through than operating costs.
Why it matters
An inefficiently high (K/L) ratio can raise the real resource cost of providing the regulated service. In the long run, this can show up as:
- higher required revenues to cover the inflated capital base,
- slower productivity improvement if incentives focus on “building the rate base” rather than cutting costs.
Practical example
A regulated utility that earns a return on its capital base may have an incentive to choose an expensive capital project (more equipment, more sophisticated infrastructure) over lower-cost operational solutions, even if both deliver similar service quality.