PANEL Procedure

The RESTRICT statement specifies linear equality restrictions on the parameters in the preceding MODEL statement. There can be as many unique restrictions as the number of parameters in the preceding MODEL statement. Multiple RESTRICT statements are understood as joint restrictions on a model’s parameters. Restrictions on the intercept are obtained by the use of the keyword INTERCEPT. RESTRICT statements before the first MODEL statement are automatically associated with the first MODEL statement, as are any RESTRICT statements that follow it but precede subsequent MODEL statements.

Currently, only linear equality restrictions are permitted in PROC PANEL. Tests and restriction expressions can be composed only of algebraic operations that involve the addition symbol (+), subtraction symbol (–), and multiplication symbol (*).

The RESTRICT statement accepts labels that are produced in the printed output. A RESTRICT statement can be labeled in two ways. It can be preceded by a label followed by a colon. This is illustrated in rest1 in the example that follows. Alternatively, the keyword RESTRICT can be followed by a quoted string, as illustrated by "rest2" in the example.

The following statements illustrate the use of the RESTRICT statement:

proc panel;
   model y = x1 x2 x3;
   restrict x1 = 0, x2 * .5 + 2 * x3= 0;
   rest1: restrict  x2 = 0, x3 = 0;
   restrict "rest2" intercept=1;
run;

If you are fitting a dynamic panel model, you can place restrictions on lags of the dependent variable by referencing the name of the dependent variable followed by an underscore and the lag order. For example,

proc panel;
   model sales = price / dyndiff;
   restrict sales_1 = 0.5;
run;

Note that a RESTRICT statement cannot include a division sign in its formulation.