National Income Determination
If G is increased, what effect does happen on the balanced
national income ?

ratprint:false; kill(all);

Gov: solve(ev(Yd=C+Inv+G, C=100+0.6*Y, Inv:40),G)[1];

load(draw)$


draw3d(color = blue,


             explicit(rhs(Gov),Y,0,600,Yd,0,600),


             contour_levels = {40,60},


             contour        = both,


             surface_hide   = true) ;

Ydem: solve(ev(Yd=C+Inv+G, C=100+0.6*Y, Inv:40),Yd);

Ydem1: ev(Ydem, G:40)[1];

Ydem2: ev(Ydem, G:60)[1];

plot2d([Y, rhs(Ydem1), rhs(Ydem2)], [Y, 0,800]);

Algebraic computation

solve(Y=rhs(Ydem1), Y);

solve(Y=rhs(Ydem2), Y);

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Contact address: Prof. Yukari Shirota, Faculty of Economics, Gakushuin University, 1-5-1 Mejiro,
Toshima-ku, Tokyo, 171-8588 JAPAN,  yukari.shirota@ipsj.or.jp