UNIFIED_LABELS = [
    'Wave_Date', 
    'NonResponse_Next_Wave', 
    'Is_Married', 
    'Age', 
    'Household_Size', 
    'Household_Income', 
    'Personal_Income',
    'Sex_Female', 
    'Is_Unemployed', 
    'Invited_Waves',
    'Nonresponse_This_Wave', 
    'Historic_Nonresponse_Rate'
    ]
