In recent years, many local governments have implemented policies to ban plastic bags in an effort to reduce environmental waste. A city council in Greenfield argues that by enforcing a ban on plastic bags, the city will significantly reduce the amount of plastic waste that clogs local waterways and contributes to pollution. For example, the council claims that statistics from nearby cities that have enacted similar bans show a 50% reduction in plastic waste within a year.
However, opponents argue that the ban on plastic bags may not have as significant an effect on plastic waste as the council suggests. They point out that the statistics from other cities are not applicable to Greenfield because those cities also implemented several other waste reduction strategies simultaneously.
Which of the following, if true, would most seriously weaken the city council’s argument?