Final answer:
The 1980s saw a large increase in juvenile crime rates in the United States, influenced by the war on drugs and the peak of the baby-boomer generation.
Step-by-step explanation:
The decade that saw a large increase in juvenile crime rates was the 1980s. During this period, the United States experienced a spike in violent crime, which coincided with the influx of crack cocaine on the streets. The increase in incarceration rates, including those in juvenile detention, was heavily influenced by the war on drugs that began during the Reagan administration. Policies such as the 'three strikes laws' and the 'Just Say No' campaign were part of the efforts to combat this issue. The demographic peak of the baby-boomer generation also contributed to the rise in crime rates.