Top prize goes to 90.5%, the proportion of plastic waste that has never been recycled

The environment, Jaffa Cakes and the reality star Kylie Jenner all feature in 2018’s statistics of the year.

Among more serious statistics relating to poverty, gender equality and climate change, the Royal Statistical Society (RSS) highlighted the power of social media and McVitie’s slashing the number of Jaffa Cakes in its Christmas tube.

Highly commended in the international category was the figure of $1.3bn, the amount wiped off Snapchat’s value within a day of a Kylie Jenner tweet critical of the platform’s redesign. The judges said that while a direct causal link could not be proven, it could be “the world’s most costly tweet”.

Dr Jen Rogers, RSS vice-president and a member of the judging panel, said the number showed “the power of celebrity” and, ironically given the RSS’s raison d’être, how it was “completely at odds to using data to evidence decisions”.

“It’s a very, very up-to-date modern statistic that shows the effect social media has in this day and age,” she said, “how this one tweet can have such a big effect. It’s astonishing.”

Kylie Jenner (@KylieJenner) sooo does anyone else not open Snapchat anymore? Or is it just me... ugh this is so sad.

The quirkiest statistic to make the highly commended list was probably the 16.7% reduction in the number of Jaffa Cakes in McVitie’s Christmas tube, which Rogers said highlighted the issue of “shrinkflation”, or “not getting as much for our money”.

Arguably the most surprising statistic to make the list was the percentage of British retail shopping – 82% – that is still in-store rather than online. Rogers said the figure, which was highly commended in the domestic category, shattered “the illusion that everyone shops online”.

The top prizes went to two statistics that highlight humankind’s relationship with the environment and attempts to avoid further damage to it.

The international winner of statistic of the year was 90.5% – the proportion of plastic waste that has never been recycled. It comes after 12 months judges said had seen “unprecedented concern about the amount of plastic in rivers and oceans”.

The UK winner was a more positive figure, 27.8%, the peak percentage of all electricity produced in the UK from solar power, achieved on 30 June thanks to a heatwave and nominated after being published in the Guardian. The figure meant solar was briefly the country’s number one power source, ahead of gas.

Rogers said: “It’s a reflection of what are the important things facing us as a population. We are becoming more and more aware of these issues surrounding us like climate change, the relationship we have with the environment, the things we can do to help the environment.”

Reflecting the dominance of environmental issues, the judges said they considered several statistics related to the country’s unusually hot summer for the UK award.

While many of the statistics make bleak reading – including those related to the gender gap, the unpunctuality of British trains and the soaring number of measles cases in Europe – the 9.5 percentage point reduction in worldwide absolute poverty over the last 10 years provided some hope. It means the proportion of people living in such hardship has more than halved since 2008.

Mona Chalabi, judge and Guardian US data editor, said that while it was important not to be complacent, “the halving of absolute poverty in a single decade is a stupendous achievement. So far we’ve heard very little about it. In the west we’ve generally focused on the bleaker situation closer to home.”

It is the second year of the RSS awards, intended as the numerical equivalent of Oxford Dictionaries’ word of the year. More than 200 nominations were made by members of the public from around the world.

• This article was amended on 19 December 2018. An earlier version gave 28.7% as the statistic for the peak percentage of electricity produced in the UK from solar power. The correct figure is 27.8%.