I am performing an univariate regression analysis by basically regressing a default rate on macro economic variables such as
$DR = \alpha + \beta GDP$
I noticed that sometimes the sign of the betas does not correspond to the economic intuition but when I add some other macro variables (unemplyoment, interest rate), then this variable has a economically intuitive sign.
I was wondering if considering such variable can be problematic ? What is the literature saying about this.
Moreover, concerning the p-value, could be also consider variables that are not significant in the univariate analysis?