As home networks see increasingly faster downstream throughput speeds, a natural question is whether users are benefiting from these faster speeds or simply facing performance bottlenecks in their own home networks. In this paper , we ask whether downstream throughput bottlenecks occur more frequently in their home networks or in their access ISPs. We identify lightweight met-rics that can accurately identify whether a throughput bottleneck lies inside or outside a user's home network and develop a detection algorithm that locates these bottlenecks. We validate this algorithm in controlled settings and report on two deployments, one of which included 2,652 homes across the United States. We find that wireless bottlenecks are more common than access-link bottlenecks—particularly for home networks with downstream throughput greater than 20 Mbps, where access-link bottlenecks are relatively rare.