They found a general trend each individual year follows: a spike just before the year followed by a downward trending long tail as it recedes into history. They also, however, noticed a trend amongst that pattern: higher peaks with shorter tails.When the team looked at the frequency of individual years, they found a consistent pattern. In their own words: “‘1951’ was rarely discussed until the years immediately preceding 1951. Its frequency soared in 1951, remained high for three years, and then underwent a rapid decay, dropping by half over the next fifteen years.” But the shape of these graphs is changing. The peak gets higher with every year and we are forgetting our past with greater speed. The half-life of '1880’ was 32 years, but that of '1973’ was a mere 10 years.
So, at a cultural level, we can see a developing ‘presentism’ in which the year we’re currently inhabiting takes on great significance, but is more quickly forgotten once it’s passed.
This agrees with a much-discussed study in Science that analyzes how citation patterns change as papers become available online:
…as more journal issues came online, the articles referenced tended to be more recent, fewer journals and articles were cited, and more of those citations were to fewer journals and articles.