Telemarketing and The UK DMA
It is believed that most, although not all, silent calls are made by telemarketing agencies.
Around 10% of dialler users in the UK are members of the Direct Marketing Association (DMA) which is an industry interest group for telemarketing in the UK. The DMA code of conduct rules that no more than 5% of the calls made per day should be silent. Many consumer groups consider this too high, and initially campaigned for this to be lowered to 3%.
Read more about this topic: Silent Call