I finally found a study
Religious Conversion in 40 Countries. The countries studied are:
Australia
Austria
Belgium
Bulgaria
Belarus
Canada
Switzerland
Chile
Cyprus
Czech Republic
Denmark
Spain
Estonia
Finland
France
Germany
U.K. (Britain)
Greece
Croatia
Hungary
Ireland
Iceland
Israel
Italy
Japan
Lithuania
Latvia
Netherlands
Norway
New Zealand
Philippines
Poland
Portugal
Romania
Russia
Slovak Republic
Slovenia
Sweden
Ukraine
United States
The results include survey nearly 70,000 people. Of that sample, 29,456 were raise Catholic and 26,866 are currently Catholic. The sample had only a small number of Muslim respondants, but did report a healthly increase as of the 485 current Muslims surveyed, only 458 reported that they had been raised Muslim, a net increase of 5.9%.
Of the survey's respondents who reported changing their religious affiliation, the survey reported that 4091 left Catholicism for something else and 1501 chose to become Catholic that had not be raised that way, for a net loss of 2590, or a 8.8% decrease. Of the 4091 who left Catholicism for something else, by far, the vast majority (3386, 82.7%) simply dropped religion altogether. The next biggest place that former Catholic found themselves was in protestant churches, 421 or 10.3% of Catholics who left Catholicism found themselves in protestant churches. Only 4 of the 4092 people who left the Catholic Church in this survey of nearly 70,000 people in 40 countries reported that they had reverted to Isalm, a figure representing less than 0.1% of all Catholics who left the Catholic faith.
The some total of all who were not raise Muslim but reverted to Islam was 55. Of this group, the largest faction came from those who had no prior religious afflication, 35 individuals or 63.6% of new Muslims had belonged to no previous religion. Among those who had a faith background, people of Jewish background were among those most likely to convert to Islam; there numbers were matched by protestant converts, each group reporting 7 who left their ranks to become Muslims. Each group them made up roughly12.7% of all new Muslims in the survey, but given that the number of Jewish adherents from which to draw is less than 1/10th ofthe number of protestant (and that aggregate Catholic numbers are larger than protestant figures), this means a significantly larger percentage of Jews converting to Islam than any other religious group. With regard to Catholicism, the actual number of new Muslims who reported that they had been raised Catholic was 4, or 7.3% of those new to Islam.
My review of the sampling process for this survey indicates that there was a bias to western cultures. So, there may be higher conversion rates among Catholics raised in non-western cultures, but certainly for those of us reporting from Europe and the Americas the reality is that what has been reflected by the personal observation of those who have noticed a larger number of Catholic reverts in their personal lives and on YouTube is going to have to find another explanation, for the reality is that Catholics in these countries are reverting to Islam at a lesser rate than all other Christians (except the Orthodox), and that it is those of no previous faith who are the majority of those adopting Islam as reverts from outside of the Ummah.