New Guidance on nonresponse weight adjustments for researchers using Millennium Cohort Study data

1 November 2010

A new CLS Working Paper is published this week giving guidance on how to adjust for nonresponse in MCS sweep 3.

CLS Working Paper 2010/6 'Nonresponse Weight Adjustments Using Multiple Imputation for the UK Millennium Cohort Study,' by John McDonald and Sosthenes Ketende, is now out.

The paper discusses nonresponse weight adjustments for sweep 3 of the UK Millennium Cohort Study (MCS).  Weight adjustments are available for monotone patterns of nonresponse, where the nonresponse weight is the inverse of the estimated probability of response based on a logistic regression model, which uses data from previous sweeps to predict response at the current sweep. For non-monotone patterns, some cases have missing data for previous sweeps and this approach cannot be easily applied. For MCS, 7.5% of the families took part in sweeps 1 and 3, but not sweep 2, i.e., a non-monotonic pattern of nonresponse for 1,444 families.

The approach to estimate a nonresponse weight for MCS sweep 3 was to use multiple imputation to impute the required missing values at sweep 2 for these 1,444 families for the logistic model for response at sweep 3. This imputation used information from sweeps 1 and 3 and only involved imputing the missing values for time-varying variables shown to be predictive of nonresponse in MCS.  This resulted in the multiple imputation of nonresponse weights at sweep 3, which can be averaged to produce a single nonresponse weight or the 10 imputed nonresponse weights can used for separate analyses and the results combined using Rubin’s rules.  The advantages and disadvantages of both approaches are discussed.