Muslim-Majority Countries vs Democracy Index Scores

Is there statistical evidence to suggest that Muslim-Majority countries are less democratic that non-Muslim-majority countries? 

According to a 2012 study by Shaheen Mozaffar, "the majority (57%) of Muslim countries are either democracies or semi-democracies, with 7% classified as Free and 50% as Partly Free, while 43% are not democracies." 

I wanted to test this myself, so I compared two datasets: one, the portion of Muslims in all countries and, two, the Democracy Index score of each country.

I then analyzed the two datasets.

On doing so, I found a moderate negative correlation indicating that a higher Muslim proportion of a country corresponds to a lower Democracy Index score:

R: -0.5773

R²: 0.3333

N: 138

p: < .00001 (result is significant at p < .01)

Are Muslim-majority countries becoming more or less democratic over time?

If we assume that a hopeful goal for Muslim-majority countries is to become more democratic, is there evidence to suggest that they are becoming so?

I looked at this as well, again using Democracy Index scores, this time for 44 Muslim-majority countries.

I weighted the scores according to the portion of a given country that is Muslim. On doing so, I found what looks to me to be bad news:

2006	3.6
2010	3.5
2014	3.8
2018	3.7
2023	3.3