Of those, some 4.7 million are considered "refugees" registered to UNRWA, meaning that the number of "refugees" have increased by a factor of eight as well.
This is due to UNRWA's dual policies of defining the descendants of Palestinian Arab refugees to be "refugees" themselves and of working against the resettlement of Arabs of Palestinian descent into their neighboring Arab countries. A problem that could have been solved decades ago instead is growing continuously because of the UNRWA, and even if there is a Palestinian Arab state declared tomorrow, there are millions of people who will have nowhere to go. This is not Israel's fault - it is squarely the fault of UNRWA and the Arab nations that want to keep Palestinian Arabs in misery as political footballs.
The study also claimed that there were 379,000 Arabs living in Jerusalem, of which 62% live in the parts that Israel redeemed in 1967. If that is true, that means that 38% of Jerusalem's Arabs live in the "Jewish" side of the city. Sounds like racism to me!