The phrase "a trend which has" is correct and usable in written English.
It can be used when discussing a specific trend that has developed or emerged over a period of time.
Example: "There is a trend which has gained popularity among young consumers in recent years."
Alternatives: "a trend that has" or "a trend which is".
This is a trend which has been speeding up in recent years: multiparty politics is here to stay.
That is part of a trend, which has been encouraged by Labour's indulgent attitude to religious education.
The success of Suzanne Collins's The Hunger Games in particular has set a trend which has been enthusiastically embraced by writers in both the UK and the US.
NC: It's a trend which has developed towards the centralisation of power in the executive which I don't think is a healthy development.
"Shoppers chose to buy a little bit more this Christmas compared with last year, a trend which has pushed sales growth up to 0.6%.
Companies, and even societies, have become less hierarchical, a trend which has been under way for decades but which seemed to accelerate in the 1990s.
Our correspondent said it was part of a trend which had seen Russian aircraft flying close to UK airspace, and there had also been similar incidents in Europe.
Here Lucretius follows a trend which had gathered pace after Epicurus' own day, the rationalistic practice associated with the name of Euhemerus of explaining the gods as pioneering human benefactors whose service had been institutionally acknowledged by formal divinization.
UKIP's Nigel Farage said the surge in support for his party was not a "freak result" but a continuation of a trend which had seen it rise in the national polls.
In the royal courts, there was increased interaction between Kannada and Telugu literatures, continuing a trend which had begun in the Hoysala period.
Hockerill, which accepts boarders and day pupils aged 11 to 19, and has many students from overseas whose families are based in the UK, also bucked a national trend which has seen a fall in the number of sixth-formers studying modern foreign languages.
