% World GDP in 1990 Geary Khamis dollars (a form of PPP)
%Note, no published GDP data for 1920 as for population

GDPoldyear =  [1;1000;1500;1600;1700;1820;1870;1900;1913;1940;1950;1951;1952;1953;1954;1955;1956;1957;1958;1959;1960;1961;1962;1963;1964;1965;1966;1967;1968;1969;1970;1971;1972;1973;1974;1975;1976;1977;1978;1979;1980;1981;1982;1983;1984;1985;1986;1987;1988;1989;1990;1991;1992;1993;1994;1995;1996;1997;1998;1999;2000;2001;2002;2003;2004;2005;2006;2007;2008];
GDPold = [105402;121208;248321;331344;371058;693502;1109684;1971881;2733190;4502584;5335860;5649957;5911278;6208987;6421224;6830521;7151719;7423896;7662286;8013450;8432822;8725317;9136466;9533552;10224886;10760252;11346932;11769155;12416761;13101913;13765940;14336492;15018417;16015152;16387996;16637925;17449530;18157093;18955430;19633163;20029995;20422612;20648355;21235635;22204271;22969599;23781918;24693769;25753178;26576359;27134084;27494233;28077301;28693574;29697950;30942239;31990498;33241788;33803487;34997327;36688285;37739365;39021274;40809563;42950182;44982587;47340576;49411106;50973935];
corrfactor = 1.1873; %Adjustment from PPP to MER based on comparison with UN and WB datasets for GDP
GDPoldcorr = GDPold./corrfactor/0.595; %0.595 represents inflation-adjustment of 1990 to 2010;
    
Pmad = GDPoldcorr*1e-6;%Maddison corrected in millions of 2010 inflation-adjusted dollars
Madend = find(GDPoldyear == 1969); %Consider only years prior to 1970 when UN stats begin
GDPseriesyear = [GDPoldyear(1:Madend)]; %Maddison years for reconstruction
GDPseriessparse = ([Pmad(1:11)]); %GDP up to 1950 for interpolation between years 
GDPseriesyearsparse = [GDPoldyear(1:11)]; %Old data up to 1950 in sparse intervals
GDPinterp = interp1(Pseriesyearsparse,Pseriessparse,1:1950,'pchip'); %Interpolation onto yearly grid
GDPMad = [GDPinterp GDPold(12:Madend)']; %Reconstructed GDP to 1969
GDPMadyear = [1:1950 GDPoldyear(12:Madend)']; %Roundabout years to 1969 but includes a check on year continuity

%This function gives an estimate of the real wealth W of civilization in 1CE
%Using Author(s) : McEvEDY, C. ;  JONES, R.
%Atlas of world population history. 1978 pp.368 pp.
% Growth rates were estimated to be 10 million per 100 years and 170
% million in 1 AD
% Assuming the wealth growth rate equals the population growth rate then 
% the wealth in year (1) is the GDP in year 1 divided by the growth rate.

etapop = 10/100/170; %Exponential growth rate in population per year
Iinit = Pseriesinterp(1)./etapop;

WMad(1) = Iinit;
for i = 2:1969;
   WMad(i) = WMad(i-1) + GDPMad(i-1);
end