The first one is the hypothesis of latent differences.

In general it’s difficult to verify socioeconomic differences in health in adolescence, because young people have a good health status.

So this hypothesis supposes that in health are already present, but not (yet) measurable with current outcome measures of health.

The prelude is visible in the unequal distribution of different determinants (i.e. behavioural/ structural factors) of health among social groups.