options crt;  ? 5e4
in cps78;  set n=550;
smpl 1,n;
olsq lnwage c fe union nonwh hisp ed ex exsq;    ? (a)
unmake @coef a1-a5 b1-b3;  ? name the coefficients
set exmaxw = -b2/(2*b3);
frml eqa agemaxw = 6 + ed1 + exmaxw;  ? use this below for values of ed1
set ed1 = 8;
  set eqa am8;  ? example of using set to evaluate the same basic equation
                ? for different values of ed1
set ed1 = 12; set eqa am12;
set ed1 = 16; set eqa am16;
print exmaxw am8 am12 am16;   ? (a - second part)
msd(noprint) fe union nonwh hisp ed;
unmake @mean m2-m6;  ? name the means; otherwise we have to use @mean(1), etc.
set lnw1 = a1 + a2*m2 + a3*m3 + a4*m4 + a5*m5 + b1*m6;
smpl 1,60;  ? special sample for years of experience
 trend ex1;  ? years of experience = 1 to 60
 ex1sq = ex1*ex1;
 age1 = 6 + m6 + ex1;
wage1 = exp(lnw1 + b2*ex1 + b3*ex1sq);
?graph wage1 age1;
graph(line,preview) age1 wage1;  ? (b) - graphics version
smpl 1,n;  ? restore full sample
edex = ed*ex;
olsq lnwage c fe union nonwh hisp ed ex exsq edex;  ? (c)
unmake @coef a1-a5 b1-b4;
frml eqc1 exmaxw = -(b2 + b4*ed1)/(2*b3);
frml eqc2 agemaxw = 6 + ed1 -(b2 + b4*ed1)/(2*b3);
set ed1 = 8; set eqc1 em8; set eqc2 amc8;
set ed1 = 12; set eqc1 em12; set eqc2 amc12;
set ed1 = 16; set eqc1 em16; set eqc2 amc16;
print exmaxw am8 am12 am16;  ? for comparison
print em8 em12 em16 amc8 amc12 amc16;   ? (c - second part)
smpl 1,60;
frml eqage age = 6 + ed1 + ex1;
set lnw1 = a1 + a2*m2 + a3*m3 + a4*m4 + a5*m5;
frml eqwage wage = exp(lnw1 + b1*ed1 + b2*ex1 + b3*ex1sq + b4*ed1*ex1);
set ed1 = 8;
 genr eqage aged8;
 genr eqwage waged8;
 graph waged8 aged8;  ? batch mode graph
set ed1 = 12;
 genr eqage aged12;
 genr eqwage waged12;
 graph waged12 aged12;
set ed1 = 16;
 genr eqage aged16;
 genr eqwage waged16;
 graph waged16 aged16;
? For a high resolution combined graph:
 graph(line,pair,preview) aged8 waged8 aged12 waged12 aged16 waged16; ? (d)
smpl 1,n;  ? restore full sample
?
?  part (e)
?
single = .not. marr;
dot single marr;
  supres smpl;
  select fe .and. . ;    ? fe and single,  fe and marr
  nosupres smpl;
olsq lnwage c union nonwh hisp ed ex exsq edex;
unmake @coef a1 a3-a5 b1-b4;
?  we assume here that the frmls  eqc1 eqc2 eqwage, and the variables
?  waged8 waged12 waged16  were defined by running parts (c) and (d) above
set ed1 = 8; set eqc1 em8; set eqc2 amc8;
set ed1 = 12; set eqc1 em12; set eqc2 amc12;
set ed1 = 16; set eqc1 em16; set eqc2 amc16;
print em8 em12 em16 amc8 amc12 amc16;
smpl 1,60;
set lnw1 = a1 + a3*m3 + a4*m4 + a5*m5;
set ed1 = 8;
 genr eqwage waged8;
 graph waged8 aged8;
set ed1 = 12;
 genr eqwage waged12;
 graph waged12 aged12;
set ed1 = 16;
 genr eqwage waged16;
 graph waged16 aged16;     ? (e)
? For a high resolution combined graph:
 graph(line,pair,preview) aged8 waged8 aged12 waged12 aged16 waged16;
smpl 1,n;
enddot;
?
delete lnwage ed ex exsq fe union nonwh hisp edex single marr;
in cps85;  set n=534;
smpl 1,n;
olsq lnwage c fe union nonwh hisp ed ex exsq;    ? (a)
unmake @coef a1-a5 b1-b3;  ? name the coefficients
set exmaxw = -b2/(2*b3);
frml eqa agemaxw = 6 + ed1 + exmaxw;  ? use this below for values of ed1
set ed1 = 8; set eqa am8;
set ed1 = 12; set eqa am12;
set ed1 = 16; set eqa am16;
print exmaxw am8 am12 am16;   ? (a - second part)
msd(noprint) fe union nonwh hisp ed;
unmake @mean m2-m6;  ? name the means; otherwise we have to use @mean(1), etc.
set lnw1 = a1 + a2*m2 + a3*m3 + a4*m4 + a5*m5 + b1*m6;
smpl 1,60;  ? special sample for years of experience
 trend ex1;  ? years of experience = 1 to 60
 ex1sq = ex1*ex1;
 age1 = 6 + m6 + ex1;
wage1 = exp(lnw1 + b2*ex1 + b3*ex1sq);
?graph wage1 age1;
? For a high resolution graph:
 graph(line,preview) age1 wage1;     ? (b)
smpl 1,n;  ? restore full sample
edex = ed*ex;
olsq lnwage c fe union nonwh hisp ed ex exsq edex;  ? (c)
unmake @coef a1-a5 b1-b4;
frml eqc1 exmaxw = -(b2 + b4*ed1)/(2*b3);
frml eqc2 agemaxw = 6 + ed1 -(b2 + b4*ed1)/(2*b3);
set ed1 = 8; set eqc1 em8; set eqc2 amc8;
set ed1 = 12; set eqc1 em12; set eqc2 amc12;
set ed1 = 16; set eqc1 em16; set eqc2 amc16;
print exmaxw am8 am12 am16;  ? for comparison
print em8 em12 em16 amc8 amc12 amc16;   ? (c - second part)
smpl 1,60;
frml eqage age = 6 + ed1 + ex1;
set lnw1 = a1 + a2*m2 + a3*m3 + a4*m4 + a5*m5;
frml eqwage wage = exp(lnw1 + b1*ed1 + b2*ex1 + b3*ex1sq + b4*ed1*ex1);
set ed1 = 8;
 genr eqage aged8;
 genr eqwage waged8;
 graph waged8 aged8;
set ed1 = 12;
 genr eqage aged12;
 genr eqwage waged12;
 graph waged12 aged12;
set ed1 = 16;
 genr eqage aged16;
 genr eqwage waged16;
 graph waged16 aged16;
? For a high resolution combined graph:
 graph(line,pair,preview) aged8 waged8 aged12 waged12 aged16 waged16; ? (d)
smpl 1,n;  ? restore full sample
?
?  part (e)
?
single = .not. marr;
dot single marr;
  supres smpl;
  select fe .and. . ;    ? fe and single,  fe and marr
  nosupres smpl;
olsq lnwage c union nonwh hisp ed ex exsq edex;
unmake @coef a1 a3-a5 b1-b4;
?  we assume here that the frmls  eqc1 eqc2 eqwage, and the variables
?  waged8 waged12 waged16  were defined by running parts (c) and (d) above
set ed1 = 8; set eqc1 em8; set eqc2 amc8;
set ed1 = 12; set eqc1 em12; set eqc2 amc12;
set ed1 = 16; set eqc1 em16; set eqc2 amc16;
print em8 em12 em16 amc8 amc12 amc16;
smpl 1,60;
set lnw1 = a1 + a3*m3 + a4*m4 + a5*m5;
set ed1 = 8;
 genr eqwage waged8;
 graph waged8 aged8;
set ed1 = 12;
 genr eqwage waged12;
 graph waged12 aged12;
set ed1 = 16;
 genr eqwage waged16;
 graph waged16 aged16;
? For a high resolution combined graph:
 graph(line,pair,preview) aged8 waged8 aged12 waged12 aged16 waged16; ? (e)
smpl 1,n;
enddot;