How did we end up confused about the numbering of the Psalms?

If you have ever tried to match the Responsorial Psalm from a Mass with a copy of the psalm from a Good News Bible, then you would have probably been confused.  I am about ready to remove the confusion. The chart posted above presents the structure of the Book of Psalms in the Old Testament in each of the Hebrew, Greek and Latin translations of the Bible. The scripture readings in the Mass have been taken from 

The problem comes about because, since the promulgation of the Latin Bible (Vulgate) in the 6th century, the Roman Catholic Church has for some reason followed the numbering and division of the psalms used by the Greek translation of the Scriptures (known as the Septuagint) whereas the scriptures used by other Christian traditions follow the division and numbering of the psalms in the Hebrew text.

Psalms 9 and 10 in the Hebrew text were combined into one psalm in the Greek Bible, so from Psalm 9 onwards, the Roman Catholic psalm numbers are one less than those in other versions. Because Psalm 147 of the Jewish psalms is split into two separate psalms in the Septuagint, the total number of psalms in both finishes up being the same—150. However, only the first 8 and the last 3 psalms agree in numbering.

Elizabeth Harrington, ‘The Problem with Psalms’, Liturgy Lines, Liturgy Brisbane, 21 August 2015