The file data_io_hw1.mat contains the following variables:

id - an id variable in the format bbbbccyyq, where bbbb is a unique
4 digit identifier for each brand (the first digit is company and last
3 are brand, i.e., 1006 is K Raisin Bran and 3006 is Post Raisin Bran),
cc is a city code, yy is year (=88 for all observations is this data set)
and q is quarter. All the other variables are sorted by date city brand.

id_demo - an id variable for the random draws and the demographic variables, of the format ccyyq. Since these variables do not vary by brand they are not repeated. The first observation here corresponds to the first market, the second to the next 24 and so forth.

s_jt - the market shares of brand j in market t. Each row corresponds
to the equivalent row in id.

x1 - the variables that enter the linear part of the estimation. Here
this consists of a price variable (first column) and 24 brand dummy variables.
Each row corresponds to the equivalent row in id. This matrix is saved
as a sparse matrix.

x2 - the variables that enter the non-linear part of the estimation.
Here this consists of a constant, price, sugar content and a mushy dummy,
respectively . Each row corresponds to the equivalent row in id.

v - random draws given for the estimation. For each market 80 iid normal
draws are provided. They correspond to 20 "individuals", where for each
individual there is a different draw for each column of x2. The ordering
is given by id_demo.

demogr - draws of demographic variables from the CPS for 20
individuals
in each market. The first 20 columns give the income, the next 20 columns
the income squared, columns 41 through 60 are age and 61 through 80 are
a child dummy variable (=1 if age <= 16). Each of the variables has
been demeaned (i.e. the mean of each set of 20 columns over the 94 rows
is 0). The ordering is given by id_demo.

The file iv_io_hw1.mat contains the variable iv which consists of an id column
(see the id variable above) and 20 columns of IV's for the price variable.
The variable is sorted in the same order as the variables in the data_io_hw1.mat.