During a recent analysis, an investment analyst estimated a multiple regression model to understand the relationship between a firm's stock returns and various independent variables including market returns, company size, and earnings growth rate. The regression output provided the following coefficients:
1. Market returns coefficient: 1.5
2. Company size coefficient: -0.2
3. Earnings growth rate coefficient: 0.8
In this context, how should the analyst interpret the coefficient for the market returns variable?