Combining this with the rapid growth in international trade, there is concern that "carbon leakage" may have undermined climate policies. This has motivated the study of consumption-based emissions (carbon footprints) in climate policy, with the initial motivation to assess the extent of "carbon leakage" (Wyckoff and Roop, 1994, Munksgaard and Pedersen, 2001, Ahmad and Wyckoff, 2003).