How Recent Is the Divergence In Taiwan- and PRC-Accented Mandarin Speech? Many have compared the differences in standard (news broadcaster) accents in of Taiwan 國語 and PRC 普通话 to the differences in British and American accents.  What linguistic factors have contributed to the divergence in these accents (particularly, what has caused Taiwanese-accented Mandarin to sound noticeably different) and when did this divergence become noticeable?  Did the divergence begin/accelerate following gradual relaxation of KMT rule in Taiwan in the 1980s?

Some clarifying points to hopefully save this question from being closed as too broad:


I am focusing on "standard" speech of CCTV/NTBS news anchors - which doesn't differ as much within either country (i.e., the speech of any two news anchors within either PRC or Taiwan will not diverge as much as the speech of any two people in the larger populations), yet is is notably different between either country (i.e., the speech of a news anchor from PRC and another news anchor from Taiwan will consistently diverge, likely in predictable ways).  The difference is particularly obvious when CCTV4, for example, includes snippets from Taiwanese news outlets narrated in speech that differs markedly from that of the PRC anchors.  A stab at cross-strait comity that ironically brings to mind the gap.
My interest is that since KMT pushed 國語 repressed use of 台语 as part of a political agenda following their retreat to Taiwan, one would think that they would have used news broadcast speech as a tool to advance this political agenda, in a similar way as the PRC does now (in the PRC case, perhaps more a desire for linguistic unification than oppression, per se).  Given the origin of KMT from Mainland (admittedly, many parts of Mainland), I would like to know whether the speech Taiwan news anchors of 40-50 years ago is (a) markedly different from the speech of modern Taiwan news anchors ; (b) if so, was it more similar then to the speech of modern PRC news anchors ; (c) if so, when did the divergence begin. 
One alternate possibility to a growing divergence over time wrt news anchor speech is that from the beginning, in Taiwan, the KMT came up with a different conception of what standard 国语 should sound like, and that standard, enforced from the getgo, was already divergent from what is currently spoken by news anchors in the Mainland.  


I was simply not around when all of this was/not taking place, so am curious to hear from folks who were.
Actually, until around the 1990s, the spoken language in official sources were very similar.

Famous singers like Teresa Teng spoke pretty much like people from China nowadays. Here's an example of an interviewee from those earlier days: https://www.youtube.com/watch?v=cWEcZvhfnzA&amp;hd=1 (There's a great quote about how Teresa Teng's songs brought comfort for those miserable mainlanders!). There's a lot more stuff from those earlier days you can search via youtube.

There are a couple of important factors as to why they diverged.
1) The northern parts of Taiwan are its political/economic center and early on home to most of the refugees from Mainland China. Because of this, they strongly emphasized standard Mandarin as a sign of status/power etc. However, on the other hand, southern Taiwan has always been home to Chinese variants different from the mainland due to the influence of the people who were there before the KMT came to power.

2) Until the 1990s, the KMT strongly enforced a 国语运动 (presumably the 国语 back then was similar to how mainland Chinese is now). This meant if you were at school, in public, in meeting involving more than 3 people and you were found to be using a (gasp) non-国语 language, you would be heavily punished (3000-10000 元).  (Here's wikipedia on this: http://zh.wikipedia.org/zh-cn/%E5%9C%8B%E8%AA%9E%E9%81%8B%E5%8B%95)

3) In the 1990s the DPP started to gain traction in south. They advocated a Taiwanization movement. They wanted to have a Taiwan distinct from China. This meant no more 国语运动 and allowing for more of the Chinese variants.

In summary, I would say that Taiwanese variant of Chinese has always had some amount of difference from the mainland. However, because of various political reasons, those variants were never heard publicly. In some aspects, they were suppressed. But with the rise of a more tolerant government and the Taiwanization movement, Taiwan wanted to carve out a distinct variant of 国语, and thus we now have quite a big difference between the mainland and Taiwan.