It's long been a contention that the advertised speeds are an "up to" rating meaning that the ISP doesn't actually have to provide that speed. Consumers generally expect that the advertised speed is the speed that they will be receiving at their house. The FCC monitors the actual versus advertised speed and has reported some data for September of last year.
According to the FCC's data, more than half of the major ISPs failed to meet the advertised download speed. An additional three meet the advertised speed when averaged over 24 hours, but fell short of the advertised speed during the peak hours of 7-11p.m. The chart of data can be seen above. Upload speeds can be seen below.
When it comes to upload, the companies performed better. Only four of the 15 companies didn't provide advertised upload speeds. It just goes to show that not all ISPs are created equal.