Evidence suggests the IQs of people in the UK, Denmark and Australia have declined in the last decade. A study by the University of Hartford claims the larger the global population becomes, the less intelligent we will be, dropping by around eight IQ points by the year 2110 - and other estimates are even more pessimistic. (Source: MAIL ONLINE)
A Mail Online (UK) article discussed recent findings by scientists showing average IQs in the UK, Denmark, and Australia have declined in the last decade, and world IQ has been declining since the 1950s:
"Opinion is divided as to whether the trend is long-term, but some researchers believe that humans have already reached intellectual peak.
Scientists including Dr Flynn think better education can reverse the trend and point out  the perceived decline could just be a blip. However, other scientists are not so optimistic.
Some believe the Flynn effect has masked a decline in the genetic basis for intelligence, so that while more people have been reaching their full potential, that potential itself has been declining.
Some have even contentiously said this could be because educated people are deciding to have fewer children, so that subsequent generations are largely made up of less intelligent people.
Richard Lynn, a psychologist at the University of Ulster, calculated the decline in humans’ genetic potential.
He used data on average IQs around the world in 1950 and 2000 to discover that our collective intelligence has dropped by one IQ point.
Dr Lynn predicts that if this trend continues, we could lose another 1.3 IQ points by 2050.
Michael Woodley, of the Free University of Brussels, Belgium, claims people’s reactions are slower than in Victorian times, and has linked it to a decline in our genetic potential."
What this article never mentions is that the beginning of the decline of worldwide intelligence begins with the slowing of white European and American birthrates in the middle of the last century and a huge increase in the world's Third World populations during the same period.

For example, black Africans have extremely low IQs when compared to Europeans (70 verses 100), therefore, the population explosion in Africa over the last several decades means an increase in the total percentage of the world's population genetically descended from low IQ African populations.

The dramatic decline of IQ in First World Western populations can be attributed to the recent mass immigration of low IQ Third World groups into those nations.
Notice that the above graph from Mail Online shows the beginning of worldwide decline in IQ as 1950 and speeding up in the preceding decades. Now, notice that the low IQ populations of Africa, India, and Latin America all saw colossal population growth at exactly the same period (LINK).
While genetically high IQ groups like White Europeans have seen population stagnations in the last 7 decades, low IQ groups have seen huge population spikes in that same time. The result: a much lower worldwide average IQ.
(Source: LINK)