["Australian Journal of Agricultural and Resource Economics, EarlyView. ", "\nABSTRACT\nThe agricultural sector's share of GDP in growing economies typically declines but, for a century from the early 1850s, Australia's did not. That trend is most evident for the former colony and now State of South Australia (SA). Moreover, that share for SA has been almost flat since 1980 as well, along with the agricultural sector's share of SA exports. This paper seeks to shed light on the forces behind the unusual evolution of these sectoral shares for SA both up to 1950 and since 1980. The extensive time series data compiled for this paper suggest various partial explanations. For 1850–1950, they include the huge arable land area per worker, clearly defined and enforced property rights in settled rural areas as the frontier of European settlement expanded, the absence of a need to do any processing of the main 19th century exports (copper, wool and wheat), a strong public agricultural research and extension system, and the absence of major mining booms after the copper finds in the 1840s and 1860s.\n"]