Please answer a question about the following article about Ashkenazi Jews:

It is estimated that in the 11th century Ashkenazi Jews composed only three percent of the world's Jewish population, while at their peak in 1931 they accounted for 92 percent of the world's Jews. Immediately prior to the Holocaust, the number of Jews in the world stood at approximately 16.7 million. Statistical figures vary for the contemporary demography of Ashkenazi Jews, oscillating between 10 million and 11.2 million. Sergio DellaPergola in a rough calculation of Sephardic and Mizrahi Jews, implies that Ashkenazi make up less than 74% of Jews worldwide. Other estimates place Ashkenazi Jews as making up about 75% of Jews worldwide.

Who made rough calculations and implied that Ashkenazi Jews make up less than 74% of the Jewish population worldwide?
Sergio DellaPergola