“…15 Benz and Tru ¨ck (2009), Chevallier (2011), Feng, Zou, and Wei (2011), and Conrad, Rittler, and Rotfuß (2012 investigated and confirmed the partially stochastic behavior of allowance prices when there is clustering of volatility (e.g., periods of high volatility). Daskalakis, Psychoyios, and Markellos (2009) and Gronwald and Ketterer (2012) allow for the possibility of price jumps, and Gronwald, Ketterer, and Tru ¨ck (2011) estimate the relationship between allowance prices and financial markets by using copulas-a method that relaxes the assumptions concerning the underlying error structure. 16 Although it is not always straightforward to interpret the results of econometric studies that are not based on theoretical or conceptual models, what is clear from this literature is that even though the scarcity of CO 2 emissions allowances is institutionally induced, the allowance market itself appears to function very much like other commodity markets.…”