That's an excellent observation, and it's a design choice that sparks a lot of debate. The short answer is: yes, they *can* be effective for specific goals, but they also come with significant trade-offs that sometimes make them less effective overall.
The primary purpose of those small, circular openings is containment. They are often called "anti-scavenging" or "animal-proof" designs. By limiting the aperture, they prevent larger items from being easily pulled out by animals like raccoons, dogs, or birds, which can scatter trash everywhere. This design also discourages people from improperly disposing of oversized household or commercial bags, forcing waste to go to more appropriate dumpsters. In this specific function—keeping contained trash contained—they perform well.
However, their effectiveness in capturing litter is where the problem lies. The fundamental rule of public waste management is that if a bin is not convenient, people will not use it. A person holding a crumpled paper coffee cup, a food wrapper, and maybe a phone will often choose the path of least resistance. If the opening is too small or requires precise aim, many will simply give up and litter. The design prioritizes stopping trash from getting *out* over making it easy to put trash *in*.
Furthermore, these bins fill up quickly because the small opening creates an airlock, preventing trash from being compacted. This leads to overflow, which is itself a major source of litter. A passerby seeing an overflowing bin is much more likely to add to the pile on the ground.
So, are they effective? It's a mixed bag. In controlled, high-foot-traffic areas where overflow is managed frequently, they can help with containment. But in many general urban settings, their inconvenience can paradoxically lead to more littering around the bin itself. Modern urban design is increasingly moving toward larger, more inviting openings paired with other solutions like frequent emptying, better signage, and public education, aiming to make the right choice the easy choice.