Important features of attraction models are that they rightfully assume that
market shares sum to unity and that the market shares of individual brands are in between
0 and 1. This complicates the econometric analysis, as we will see below. Typically, an
attraction model can be written as a system of equations concerning all market shares,
and the parameters can be estimated using standard methods, see for example Cooper
(1993) and Bronnenberg et al. (2000).