Yes they have, and thanks for noticing. Normally drug addiction expands according to a logistical growth pattern, meaning it gets exponentially worse year after year until it reaches a plateau where the losses are equal to the new additions.
Thankfully our War on Drugs has kept the normal and natural growth of drug addiction from increasing. It has been held down to two percent of the population for nearly a hundred years.
No matter how you slice it, that has been an incredible success.
Now there are some incredibly ignorant and stupid people who think that because there is a small amount of ongoing drug usage occurring in our country, that this means the entire effort is a complete failure. These people are simple minded and foolish and should not be listened to.
They have just never had the necessary education or thinking ability to grasp what would happen if we hadn't had a drug war. Like a cow, they are of the simple minded "The Grass is always greener on the other side of the fence" mindset. They want legalized drugs because they have no grasp of what the society would be like if they got what they wanted.
Two percent may simply be modern America's plateau (carrying capacity).