What is the significance of the horizontal line in Figure 2-2? Why do you think oil was not modeled to at least equal one but wood was?

10- Wood 1. Oil Coal F/(1 - F) Gas 0.1 - Nuclear Solar-Fusion 0.01- 1860 1880 1900 1920 1940 1960 1980 2000 2020 2040 2060 2080 2100 Fig. 2-2. World primary energy substitution Sources: 1850-1994 from online data developed by Nakicenovic (1984) and updated for use in Grubler (1998) These data are no longer available online but are said to be available from Publications Department, International Institute for Applied Systems Analysis, Laxenburg, Austria. The 1995-2010 data has been updated from US EIA (n.d.d) and World Bank (n.d.). Note: The black line is F/(1 - F) for actual consumption and the dotted white line is its smoothed and projected consumption. Fis the fuel share