Aves and a sister group, the clade Crocodilia, contain the only living representatives of the reptile clade Archosauria. During the late 1990s, Aves was most commonly defined phylogenetically as all descendants of the most recent common ancestor birds and Archaeopteryx lithographica.9 However, an earlier definition proposed by Jacques Gauthier gained wide currency in the 21st century, and is used by many scientists including adherents of the Phylocode system. Gauthier defined Aves to include only the crown group of the set of birds. This was done by excluding most groups known only from fossils, and assigning them, instead, to the Avialae,10 in part to avoid the uncertainties about the placement of Archaeopteryx in relation to animals traditionally thought of as theropod dinosaurs.such as a person or a household. According to what the economist Nicholas Barr describes as the ’classical definition of income’ (the 1938 Haig-Simons definition): ’income may be defined as the... sum of (1) the market value of rights exercised in consumption and (2) the change in the value of the store of property rights...’ Since the consumption potential of non-monetary goods, such as leisure, cannot be measured, monetary income may be thought of as a proxy for full income.3 As such, however, it is criticizedby whom? for being unreliable, i.e. failing to accurately reflect affluence (and thus the consumption opportunities) of any given agent. It omits the utility a person may derive from non-monetary income and, on a macroeconomic level, fails to accurately chart social welfare. According to Barr, ’in practice money income as a proportion of total income varies widely and unsystematically. Non-observability of full-income prevent a complete characterization of the individual opportunity set, forcing us to use the unreliable yardstick of money income.sell btc 78218