“…has improved only slightly. Some of the more prominent works on the specification and estimation of Engel curves are Engel (1857), Working (1943), Nicholson (1949), Prais and Houthakker (1955), Leser (1963), Kakwani (1978), Bewley (1986), Giles and Hampton (1985), Aasness and Rodseth (1983), Haque (1984Haque ( , 1988, Banks et al (1997) and Beneito (2003).…”