documentclass{article}
usepackage[utf8]{inputenc}
usepackage{tikz} % 引入tikz宏包
usetikzlibrary{calc} % 计算坐标轴

begin{document}
begin{tikzpicture}[domain=0:5,scale=1.5,thick] % scale 实现缩放，所以不必担心绝对坐标的问题
% 定义供给曲线和需求曲线的参数
defdint{4.5} %需求曲线Y轴的截距
defdslp{-0.5} %需求曲线的斜率
defsint{1.2} %供给曲线Y轴的截距
defsslp{0.8} %供给曲线的斜率
    %定义供给曲线和需求曲线
    defdemmand{x,{dslp*x+dint}}
    defsupply{x,{sslp*x+sint}}

% 标记坐标点
coordinate (ints) at ({(sint-dint)/(dslp-sslp)},{(sint-dint)/(dslp-sslp)*sslp+sint});  %均衡点
coordinate (ep) at (0,{(sint-dint)/(dslp-sslp)*sslp+sint}); %均衡价格纵坐标
coordinate (eq) at ({(sint-dint)/(dslp-sslp)},0); %均衡数量横坐标
coordinate (dint) at (0,{dint});
coordinate (sint) at (0,{sint});

% 绘制坐标轴
draw[->] (0,0) -- (0,6) node[above] {$P$};
draw[->] (0,0) -- (7,0) node[right] {$Q$};

% 绘制供给和需求曲线
draw[thick, color=blue] plot (demmand) node(right) {$D(p)={45}-5p$}; % 需求曲线
draw[thick, color=red] plot (supply) node(right) {$S(p)=12+8p$}; % 供给曲线
draw[dashed] (ints) -- (ep) node[left] {$p^*$};
draw[dashed] (ints) -- (eq) node[below] {$q^*$};

% 标示均衡点
fill[purple] (ints) circle (2pt);
end{tikzpicture}
end{document}

clear
set obs 200

gen q = _n
gen p = (20-q)/2
keep if  p >0
gen p1 = 2
gen p2 = 3

line p q || (rarea p p1 q if q <= 16 & p <= 3, sort color(gray)) || ///
	(rarea p1 p2 q if q <= 14,sort color(gray)), ///
	scheme(qleanmono) plotregion(margin(sides)) legend(off) ///
	title("消费者剩余的变化") ///
	ytitle("p") xtitle("q") ///
	yline(2,lp(dash)) xline(16,lp(dash)) ///
	yline(3,lp(dash)) xline(14,lp(dash)) ///
	ylabel(0(2)10 2 3) xlabel(0(4)20 14 16) ///
	text(6.5 10  "{it:D(P) = 20 - 2*P}") ///
	text(2 17 "{it:(16,2)}")  ///
	text(3 15 "{it:(14,3)}") ///
	text(2.5 6 "{it:S =½(14+16)*1 = 15 }")

begin{tikzpicture}[domain=0:5,scale=0.4,fill opacity=0.6]
defdint{20}     %Y-intercept for DEMAND.
defdslp{-2}     %Slope for DEMAND.

defdemand{x,{dslp*x+dint}}
% DEMAND
draw[color=blue] (20,0) -- (0,10) node[right] {$D(p) = 20 - 2p$};
% CS
draw[dashed] (0,3) -- (14,3);
draw[dashed] (0,2) -- (16,2);
fill [fill=red] (0,3) -- (14,3) -- (16,2) -- (0,2);
% Draw axes
    draw[->] (0,0) -- (25,0) node[right] {$Q$};
    draw[->] (0,0) -- (0,15) node[left] {$P$};
end{tikzpicture}

% 需求价格弹性
begin{tikzpicture}[scale=3]

% 坐标轴
draw [<->,thick] (0,2) node (yaxis) [above] {$P$}
    |- (3,0) node (xaxis) (above) {$Q$};

    % 绘制两条直线
    draw[color=white] (0,0) coordinate (a_1) -- (2,2) coordinate (a_2);
    draw (0,1.5) coordinate (b_1) -- (1.5,0) coordinate (b_2) node[below] {$Demand$};

    % 计算直线交点，并储存为c
    coordinate (c) at (intersection of a_1--a_2 and b_1--b_2);

    % 标示交点
    fill [red] (c) circle (1pt);

    draw[->,dashed] ($(c)+(0,0.15)$) -- ($(c)+(-.7,0.85)$);
    draw[->,dashed] ($(c)+(0.15,0)$) -- ($(c)+(0.85,-0.7)$);

        fill[blue] (0.5,1.5) node {Elastic};
        fill[blue] (1.6,0.5) node {Inelastic};

    draw[->] (1.5,1.5) node[label=above:Unitary Elastic] {} -- ($(c)+(.1,.1)$);

end{tikzpicture}

%                         TikZ code: An excise tax
begin{tikzpicture}[domain=0:5,scale=1,thick]
usetikzlibrary{calc}                                %allows coordinate calculations.
usetikzlibrary{decorations.pathreplacing}           %allows drawing curly braces.

% Define linear parameters for supply and demand
defdint{4.5}      %Y-intercept for DEMAND.
defdslp{-0.5}     %Slope for DEMAND.
defsint{1.2}      %Y-intercept for SUPPLY.
defsslp{0.8}      %Slope for SUPPLY.

deftax{1.5}       %Excise (per-unit) tax

% Define Supply and Demand Lines as equations of parameters defined above.
  defdemand{x,{dslp*x+dint}}
  defsupply{x,{sslp*x+sint}}
  defdemandtwo{x,{dslp*x+dint+dsh}}
  defsupplytwo{x,{sslp*x+sint+ssh}}


% Define coordinates.
    coordinate (ints) at ({(sint-dint)/(dslp-sslp)},{(sint-dint)/(dslp-sslp)*sslp+sint});
    coordinate (ep) at  (0,{(sint-dint)/(dslp-sslp)*sslp+sint});
    coordinate (eq) at  ({(sint-dint)/(dslp-sslp)},0);
    coordinate (dint) at (0,{dint});
    coordinate (sint) at (0,{sint});

    coordinate (teq) at  ({(sint+tax-dint)/(dslp-sslp)},0); %quantity
    coordinate (tep) at  (0,{(sint+tax-dint)/(dslp-sslp)*sslp+sint+tax}); %price
    coordinate (tint) at  ({(sint+tax-dint)/(dslp-sslp)},{(sint+tax-dint)/(dslp-sslp)*sslp+sint+tax}); %tax equilibrium

    coordinate (sep) at (0,{sslp*(sint+tax-dint)/(dslp-sslp)+sint});
    coordinate (sen) at ({(sint+tax-dint)/(dslp-sslp)},{sslp*(sint+tax-dint)/(dslp-sslp)+sint});

% DEMAND
    draw[thick,color=blue] plot (demand) node[right] {$P(q) = -frac{1}{2}q+frac{9}{2}$};

% SUPPLY
    draw[thick,color=purple] plot (supply) node[right] {Supply};

% Draw axes, and dotted equilibrium lines.
    draw[->] (0,0) -- (6.2,0) node[right] {$Q$};
    draw[->] (0,0) -- (0,6.2) node[above] {$P$};
    draw[decorate,decoration={brace},thick]  ($(sep)+(-0.8,0)$) -- ($(tep)+(-0.8,0)$) node[midway,below=-8pt,xshift=-18pt] {tax};

    draw[dashed] (tint) -- (teq) node[below] {$Q_T$};
    draw[dashed] (tint) -- (tep) node[left] {$P_d$};
    draw[dashed] (sen) -- (sep) node[left] {$P_s$};

end{tikzpicture}

begin{figure}
begin{tikzpicture}[scale=0.8]
tiny
draw (0,0) -- (8,0) node [below] {Quantity, units};
draw (0,-0.5) -- (0,5) node [above] {Cost per unit, $};
draw (0.2,5) to [out=270,in=172] (2.6,0.4);
draw (2.6,0.4) to [out=350.5,in=178] (7,0.1);
node [right] at (7,0.5) {$AFC$};
draw (0.3,5) to [out=280,in=150] (2,2.1);
draw (2,2.1) to [out=330,in=200] (7,2);
node [right] at (7,2.3) {$ATC$};
draw (0,2) to [out=340,in=200] (7,1.8);
node [right] at (7,1.8) {$AVC$};
draw (0,2) to [out=315,in=240] (7,5);
node [right] at (7,5) {$MC$};
end{tikzpicture}
caption{Short-run unit cost curves}
end{figure}

% Slutsky Decomposition
usetikzlibrary{decorations.pathreplacing}
begin{figure}
begin{tikzpicture}[scale=1.2]
draw [thick] (0,0) -- (8,0);
draw [thick] (0,0) -- (0,5);
node [right] at (8,0) {$x_1$};
node [above] at (0,5) {$x_2$};
draw [thick] (1.7,4.2) to [out=310,in=160] (5.4,1.5);
draw [thick] (0.6,4) to [out=295,in=165] (3.5,1);
draw [thick] (1.4,3.2) to [out=290,in=155] (3.5,1.3);
node [right] at (6.5,0.9) {$C$};
draw [thick] (0,4.6) -- (7.5,0);
draw [thick] (0,4.6) -- (3.15,0);
draw[dashed](1.4,2.5)--(1.4,0);
draw[dashed](3.4,2.5)--(3.4,0);
draw [thick] (0,3.4) -- (5.4,0);
draw[dashed](2.4,1.9)--(2.4,0);
node [above] at (2.4,2) {$x^B$};
draw[fill] (2.4,1.9) circle [radius =0.06];
node [left] at (1.3,2.5) {$x^A$};
draw[fill] (1.4,2.5) circle [radius =0.06];
node [right] at (3.2,3) {$x^C$};
draw[fill] (3.4,2.5) circle [radius =0.06];
node [right] at (0.5,4.6) {$C$};
node [right] at (-0.1,4) {$A$};
node [left] at (2.9,0.2) {$A$};
node [right] at (4.3,0.2) {$B$};
node [right] at (-0.1,3.1) {$B$};
draw [decorate,decoration={brace,amplitude=4pt, mirror},xshift=0pt,yshift=-3pt]
(1.4,0) -- (2.4,0) node [black,midway,yshift=-.5cm] {footnotesize $SE_1$};
draw [decorate,decoration={brace,amplitude=4pt, mirror},xshift=0pt,yshift=-3pt]
(2.4,0) -- (3.4,0) node [black,midway,yshift=-.5cm] {footnotesize $IE_1$};
end{tikzpicture}
caption{Slutsky decomposition}
end{figure}