 Although no longer seen as a primarily descriptive theory, the economic approach appears to rationalize established doctrines that competing views struggle to explain. The approach seems tailormade to explain the law’s encouragement of “efficient breach” (discussed earlier, in  §1.1).  Though even here there are puzzles. It remains unclear why contract law is unwilling to promote efficiency through orders of specific performance (Ayres &amp; Klass 2017). After all, it is likely costly to deal with an unwilling counterparty forced to perform, so promisees will usually seek specific performance only when expectation damages are genuinely undercompensatory or hard to calculate (Schwartz 1979). At the very least, an efficient contract law should allow parties, ex ante, to contract for the specific performance remedy or even for supra-compensatory “penalties” that assure performance by requiring damages upon breach that exceed the promisee’s expectation interest (see discussion in Edlin 1996; Edlin &amp; Schwartz 2003; Shavell 1980). But, in fact, the law does not condone such agreements, even between sophisticated parties (R2: §356; see, e.g., Lake River v. Carborundum (1985)). A possible explanation is that penalty clauses enable inefficient collusion by established firms to keep new entrants out of markets.