"Slavery was abolished → people had to be hired"

This is where we need to distinguish logical consequence from a genuine historical inference.

Slavery was abolished.

Therefore former slaves were no longer legally slaves.

That is essentially a definitional/logical consequence.

But:

Slavery was abolished.

Therefore former slaves had to be hired as wage laborers on plantations.

That is not simply contained in the definition of abolition.

Several additional propositions have entered:

plantations continued operating;

they still required labor;

former slaves remained available as workers;

employers needed a new labor arrangement;

wage labor was one resulting arrangement.

That is much more properly called an inference.

My distinction is therefore useful:

Logical consequence: follows directly from the meaning of the proposition.

Inference: reaches a further proposition by connecting the proposition with other knowledge or assumptions.