What is the fine-grained topic of the following text: According to new figures released by the Society of Motor Manufacturers and Traders (SMMT), 495,127 grey cars were registered in 2018, giving it a whopping 20.9 per cent market share, an increase of 1.2 per cent compared to the year before. Only return the topic.
Registration of grey cars in 2018 according to SMMT figures