Exponential growth in chemistry. Data reflects registered a substances; and b abstracts on record at Chemical Abstracts Service at year end . No substances data is available for years 1977–1979. Black dashed line indicates time of random sampling of 28,963 structures from the 593,071 individual structures in the Chemical Abstracts Registry System . Gray dashed line indicates time of the ‘augmented atom’ analysis by Adamson et al. on this subset . Numbers for abstracts on record include papers, patents and books.