The Market Implementation Committee last week approved an issue charge to consider modifying the algorithm used for publishing supply curves from the annual capacity auction.

The vote followed MIC’s approval in June of a problem statement by Jason Barker of Exelon to seek improvements to the supply curve currently produced by the Market Monitor, which masks individual price-quantity offers. Barker said the current curves — a compromise intended to balance transparency against disclosure of commercially sensitive data — aren’t accurate enough for use in analysis. (MIC Seeks Better Way to Draw Capacity Supply Curve.)

The current method is the result of a Federal Energy Regulatory Commission order in a dispute over PJM’s proposal to publish price-quantity pairs after the 2010 Base Residual Auction. Constellation Energy and the monitor said that the data could be used to reconstruct participants’ offers in the SWMAAC locational deliverability area because of the concentration of generation ownership.

“We’re not opposed to providing additional granularity in the supply curve,” Market Monitor Joseph Bowring told MIC last week. But he cautioned that the FERC order made clear the commissioners’ “preference to err on the side of not providing information that could result in market power and collusion.”

A presentation by the monitor concluded that the moving average alternative suggested by Exelon is “unlikely to pass through the point at which supply equals demand because supply is an increasing function.”

Instead, Bowring offered an alternative to divide the supply curve into segments of equal megawatts, plot the average price within each segment and force the adjusted line through the clearing point. The monitor said the proposal will more closely track the true offer curve as the magnitude of jumps in supply decreases.