options crt;  ? 3e6
in update;
smpl 1,99;
lnc70 = log(cost70/pf70);
lny70 = log(kwh70);
lnp170 = log(pl70/pf70);
lnp270 = log(pk70/pf70);
msd kwh70;
in nerlov; smpl 1,145; msd kwh;  ? (a)
in; smpl 1,99;
olsq lnc70 c lny70 lnp170 lnp270;
frml eqr r = 1/lny70;
analyz eqr;  ? (b)
lny2 = lny70*lny70;
olsq lnc70 c lny70 lny2 lnp170 lnp270;
  rename @ssr ssrunr;
diff = lnc70 - lny70;  ? for f-test of lny70 coefficient=1
   ? (could also do a t-test for this; would be easier)
olsq(silent) diff c lnp170 lnp270;
  set df2 = @nob - 5;
  set fstat = (@ssr-ssrunr)/2/(ssrunr/df2);
cdf(f,df1=2,df2=df2) fstat;  ? (c)
trend t;
group = 1+int((t-1)/20);  ? this is an easy way of making a group ID variable
dummy group;
dot 1-5;
  select group.;
  olsq lnc70 c lny70 lnp170 lnp270;
  analyz eqr;  ? (d)
enddot;