It's used to chalking up gains, but the big number being marked at the London Stock Exchange yesterday was the 30th anniversary of the FTSE 100 index.
Appropriately enough it celebrated the milestone with a day that ended in the black, with shares creeping up by 12 points.
The FTSE 100 replaced the FT30 as the main indicator for the performances of companies listed on the London Stock Exchange on January 3 1984.
Today, the combined value of its constituents stands at £1.87 trillion, more than ten times higher than the market capitalisation total of £164 billion in December 1985 – the first available data.
The index has weathered the miners' strike, the Big Bang of market deregulation in 1986 and the Black Monday crash of 1987, as well as the 1990's dotcom boom and the financial crisis in more recent years.
But only 30 of the original companies, including BP and Marks & Spencer, remain on the list, which is composed of the 100 biggest London-listed firms by market value.