There is no doubt that Ann's patrilineal line great-grandfather, David DAVIES (1855-1925), was a coal miner — living in the village of Nantyffylon, near Maesteg, Glamorgan, Wales.  The issue is whether his son, David Thomas DAVIES (1882-1955) — the immigrant, first to Ontario, Canada, in 1927, then to Michigan — was actually an impoverished coal miner.

One such assertion is made in an article at BBC News:  Ann Romney's Welsh Ancestry Explored., where is says,

In his first census, at the age of 8 in 1891, David Thomas and his younger brother are given occupation, "scholar" (a.k.a., "student").  I think the fact that the boys are being educated, instead of working in the mines, has  significance for David Thomas's life and the lives of his descendants.

In his second census, at the age of 18 in 1901, David Thomas and his three younger brothers are not given occupations, which implies they are not working in the mines, but going to school.  His father and uncle are both enumerated as coal miners.

In the 1911 census, his father and younger brothers are all listed as coal miners.  Whether our subject shows up as one in 1921 remains to be seen.

The first mention I have of his adult occupation is in the ship's manifest when he made the crossing from Southampton to New York in 1927, which gives his occupation as "mechanic."  He moved from there to Ontario to Michigan.  I think it's significant that he did not immigrate to one of the coal mining regions of Pennsylvania or West Virginia as did so many Welsh coal miners.

The next mention we have of his occupation is in the 1930 census of Detroit, Michigan, where he is enumerated as a pipe-fitter in an auto parts factory.

David's journey to the New World and employment in Detroit gave his son (Ann's father), Edward Roderick DAVIES, the opportunity for an education at the General Motors Institute of Technology, which led to him becoming a wealthy industrialist.  So, yes, Ann's family is another story of the American dream.

Lastly, and while no one would minimize the hard life of a Welsh coal miner, it doesn't appear they were impoverished.  David Thomas's father — Ann's great-grandfather — left an estate of £275 in 1925, not a fortune, but not penniless, either.

In the 1911 Census of Wales, there is a David Thomas DAVIES (æ 25, b. Bettws, Glamorgan) living at 13 Victoria St., Caerau, Higher Llangynwyd Civil Parish, ED 2, Maesteg Sub-Dist., Brigden Dist., Glamorgan (Images 214-215 of 831) with his widowed father, Thomas DAVIES (æ 53, b. Cowbridge), and siblings Margaret Anne (æ 20, b. Llangeinor), Elizabeth (æ 18, b. Bettws), and Ellen (æ 15, b. Bettws).  This is clearly not our subject.

Both of our subject's parents, David DAVIES (æ 57, b. Maesteg) & Elizabeth DAVIES (æ 56, b. Nantyfflon), are living and enumerated in Nantyffylon, with children William Ed DAVIES (æ 27, b. Nantyffylon) and Emris DAVIES (æ 21, b. Nantyffylon).  Our subject was also born in Nantyffylon and this is his known family; unfortunately he isn't with them.  As an adult unmarried male (æ 28), it would not be unusually to find our subject "working out."

I could not find Mrs. ROMNEY's paternal grandfather, David Thomas DAVIES, in the 1911 Census of Wales, which is too bad because it may be our one chance to find him in the census as an adult before he emigrated to the U.S. — at least until the 1921 Census of Wales is released in 2022.

There are over 7000 David DAVIES'es indexed in Wales in 1911, with over 2500 of them born in Glamorgan.  As David Thomas was born in Nantyffylon, Maesteg, Glamorgan, in 1882, I confined my search to David's born in Glamorgan within two years of 1882.  If his birthplace is entered incorrectly on the census forms, I don't believe there's any hope of finding him — or proving it's him if we do find an otherwise plausible record.

I did one of the most exhaustive census searches (in the index at Ancestry.com) I have ever done — up to and including browsing through every page in the Enumeration District where his parents were living (Cwmdu, ED 7).

The index at Ancestry is very hard to use, so to be absolutely certain I hadn't missed the David Thomas DAVIES mentioned in the BBC article , I browsed the census records for the full length of Victoria St., from the REES family at #1 (Image 182 of 831) to the MORGAN family at #102 (Image 411 of 831), and found no alternative — so the BBC article was, indeed, referring incorrectly to the one at #13 Victoria Street. 

I've included the results of my search in a table, below, as confirmation that I did it and in case it might aid other working on DAVIES in some way.

In the 1911 census, a location could consist of a Registration District and a Registration Sub-district, each with a name and number, and a numbered Enumeration District.  It would have had both a Civil Parish and an Ecclesiastical Parish. It could be a Ward within a Borough or a Borough within an Urban District, or it could be in a Rural District.  And lastly, it would be in a parliamentary borough or division.

What makes it more complicated is that one name (e.g., Maesteg) might refer to the village or borough, the urban district or borough, the registration district or sub-district, or civil parish.  The fact that most genealogists drop the qualifiers on locations means locations given in genealogies are frequently ambiguous.  For genealogical purposes, it would be most useful if the focus was on the village name — so stated as the village name — as the most precise and generally unchanging name.