Answer:
Southern planters saw the large slave populations in the Northern colonies as a clear example to follow
Step-by-step explanation:
Southern planters did not purchase salves from the 1660's onwards because they saw large slave populations in the Northern colonies. The reason why is that the Northern colonies never had such large slave populations.
Some states did have a considerable slave population: for example New York and Pennsylvania, but it never reached the scale of the Southern planations.
The reason why is that the Northern climate is not suitable for those plantations, and as a result the economy of the northern states was based on othery types of agriculture.