This study looks at all public limited companies (PLC) registered in the United Kingdom. The aim of this study is to provide an overview of the key movers and shakers of PLCs. Only key data has been isolated, particularly the company's net worth and total assets, but also their full name, date incorporated, registered office, activities, shareholders, directors (with date of birth, occupation and nationality) and number of employees. Two indicators of size are used: net worth and total assets. These are preferable to turnover which is influenced by profit margins and whether the companies are capital or labour intensive. A short summary of the PLCs in the United Kingdom: A PLC can be either an unlisted or listed company on the stock exchange. Companies must include the words 'public limited company', 'PLC' or 'plc' as part of its name. Welsh companies may choose 'cwmni cyfyngedig cyhoeddus', 'CCC' or 'ccc'. The PLC form was introduced in the Companies Act 1980; prior to this, all limited companies had the suffix 'Limited' or 'Ltd'. A PLC must have a minimum allotted share capital of £50,000, a quarter of which, £12,500, to be paid up. The main advantage of a PLC is the ability to raise capital by issuing public shares. The main disadvantages are more regulation, higher accounting transparency and vulnerability to takeovers. The Unlisted Securities Market (USM), which ran from 1980 to 1996, was a stock exchange set up by the London Stock Exchange to cater for companies too small to qualify for a full listing. The USM allowed companies to be traded which did not have the full three year trading history required by the main market, or which wished to float less than 25% of their share capital. The Alternative Investment Market (AIM) was set up in June 1995 and USM companies could move their quotation to AIM or delist. Since 1995, over 3,000 companies have joined AIM raising more than £60 billion in new and further capital. JP Jenkins provides a matched bargain dealing facility for unlisted companies such as Millwall Holdings PLC and Rangers International Football Club PLC. The London Stock Exchange (LSE) has 1,450 companies listed and AIM 1,150 companies.