Looking on the internet deeply has found these results:

they have not given much thought is the most popular phrase on the web.

they did not given much thought 11 results on the web	they have not given much thought 1341 results on the web More popular!
Some examples and use cases from the internet:	Some examples and use cases from the internet:
Sep 29, 2014 ... Some medical device companies have designed cutting edge devices, but experts says they did not given much thought to the potential�...	May 8, 2015 ... They have not given much thought to the areas in which they could help Cameron to achieve some of what he wants. A successful British�... ... thus be a way of making real and tangible those experiences that people have read or heard about previously but to which they have not given much thought. Individual Volatility but Collective Stability The opinions expressed by individuals, when surveyed on political issues to which they have not given much thought,�... 4 days ago ... They have not given much thought to the areas in which they could help Cameron to achieve some of what he wants. A successful British�...

they did not given much thought

11 results on the web

they have not given much thought

1341 results on the web

More popular!

Sep 29, 2014 ... Some medical device companies have designed cutting edge devices, but experts says they did not given much thought to the potential�...

May 8, 2015 ... They have not given much thought to the areas in which they could help Cameron to achieve some of what he wants. A successful British�...
... thus be a way of making real and tangible those experiences that people have read or heard about previously but to which they have not given much thought.
Individual Volatility but Collective Stability The opinions expressed by individuals, when surveyed on political issues to which they have not given much thought,�...
4 days ago ... They have not given much thought to the areas in which they could help Cameron to achieve some of what he wants. A successful British�...