This beats or equals 95.0% of test takers.
Not bad, but how come there so many middle eastern countries on the list?
As mentioned above, this is mostly a list of countries that were not colonized by Europe prior to 1900. The Arabian peninsula fit that bill because, prior to the discovery of oil there in the 1930s, nobody gave a crap about the Arabian peninsula. It's mostly useless desert. Slavery was allowed to persist in Arabia, an important facet of Arab culture enshrined in and supported by Islam, independent of emancipation movements in the Western world, because of this fact. Once Westerners began trading with these countries they started to put pressure on them to abolish slavery.
Following independence slavery was officially abolished throughout Niger. But there was a similar problem with many administrators looking the other way and allowing it to continue in practice. It wasn't until 2003 that slavery was specifically criminalized.