The Navigation Acts had different impacts on trade in the colonies at different places and times. For much of colonial history, they did not have a great impact. However, this was largely because the British did not try to enforce them for much of the time.
When the Navigation Acts were first passed, they hurt trade in many parts of the colonies. For example, Virginia had sold much of its tobacco to Dutch traders. Now it could not, which lowered the prices that it could charge.
At some times and in some places, the Navigation Acts simply changed the way trade was carried out. Before the acts were passed, trade was carried out openly. After the acts passed, traders had to change their ways. They had to resort to trading illegally (smuggling). Trade still occurred, but it was clandestine and illegal instead of open and legal.
At still other times, the acts had very little impact. This was because the British government did not try very hard to enforce them. The American colonies did a great deal of trade with Britain, thus keeping the mother country happy. It therefore did not try too hard to keep them from trading illegally with places like French colonies in the Caribbean. Thus, trade was not greatly affected.
After the French and Indian War, the British government really cracked down on illegal trade. This seriously restricted trade in the colonies. Because of this, it helped bring about the Revolutionary War.
So, we can see that the Navigation Acts had different effects at different times. Sometimes the acts curtailed trade, sometimes they led to more smuggling, and sometimes they had very little effect at all.
The Navigation Acts were basically restrictive trade laws which affected trade in the colonies in a negative manner, For example:
1. It gave rise to monopolies
2. It promoted smuggling and illegal trade
3. There were many taxes
4. Both export volume and prices were reduced
5. Colonies paid higher prices and earned smaller incomes.