Numbers are taken from the 1901 census (because no earlier complete census is available). I have shown figures of one Dowling per thousand of population as this better shows distrubution. Raw number contains no context of the remaining population and, consequently, show a bias to where Dowlings are now rather then where they figure most strongly. This translates into more Dowling's numerically in Dublin but gives no clue as to origin.
The Dowling per thousand approach shows wonderfully the bias towards the West of the River Barrow in the midland counties. It also shows nicely the slight increase in Kerry where Dowlings were transported in the 17th century. (Note: this does not include variations on the name)