For example, national accounts statistics that incorporate a gender perspective take into account both women’s and men’s contribution to all social and economic areas, including unpaid work. The word “sex" refers to biological differences between women and men. Biological differences are fixed and unchangeable and do not vary across cultures or over time. “ Gender”, meanwhile, refers to socially-constructed differences in the attributes and opportunities associated with being female or male and to social interactions and relationships between women and men.