If all regressors are identical, the results are identical to those obtained by running separate OLS, which would yield consistent but less efficient estimators. Thus, the husband's and wife's shares must sum to 1. Furthermore, the respondent's labour force participation may directly affect the amount of time spent in housework for reasons unrelated to bargaining power. Education can affect a person's outside or fallback options. More specifically, a wife's education level relative to her husband's (so-called education gap) may determine her relative bargaining strength in the household. However, the effect is likely to be non-linear in that as the gap increases (with the husband being more educated), so does the relative bargaining power of the husband.