After converting this from minutes into hours, we divide the total monthly income, as calculated using the midpoint of the income category group, by the total monthly hours of market work to obtain the estimated hourly wage. Non-working individuals are assumed to have zero hourly wage. For example, if the wife reports 5 hours of market work a day and has a monthly income of 1,000-2,000 RMB category, we calculate her hourly wage as: 1,500/(5x22) = 13.64 RMB.