Thanks for asking, Martin. I should have added the source in the article.
I’ve received the information from here:
I did check the source you’ve mentioned. The information there is based on a survey conducted in the U.S. only, and we are speaking for a global audience.
Although the data mentioned on Spiegel is from 2017 (I didn’t get any fresh stat), I believe that the percentage of people reading online reviews now has certainly not decreased, if not increased.