By way of revision let us recall that the essential basis of radiocarbon dating is comparison between the carbon-14 activity measured in the sample and the activity presumed to have been present in the sample when it was formed. If in reality the starting activity was higher than presumed then the date obtained will be too recent, and vice versa. An underestimation of 1% in starting activity leads to an age deficit of about 80 years irrespective of the date.