Culturally neutral, minimal adaptation required.

Psychometrically sound, including concurrent, discriminant and predictive validity.

Sensitive to child age and environment.

Amenable to improvements.

Feasibly administered.

Minimal training required.

Interpretable by policy makers.

Open access, no/limited cost (training, materials).

Could be used to develop norms.

Creation of a common data set from three initiatives (IYCD, CREDI and D-score).

Harmonisation of data sets generated from the use of 22 instruments (2275 items) administered to 73 222 children (a total of 109 079 visits, and unique child/age combinations) within 51 cohorts.

Items selected by matching ratings of subject matter experts with instrument prototypes based on construction of a latent scale of childhood development using optimal statistical modelling approaches (Rasch vs a two-parameter model).

Simulations of expected psychometric properties of the instruments based on existing data set.

Field testing to verify the properties of both instruments, in accordance with the predefined characteristics.