The phrase "plunged dramatically" is correct and can be used in written English.
It is typically used to describe a sudden and significant change or movement in something, often in a theatrical or exaggerated manner. Example: The stock market plunged dramatically, causing panic among investors.
Earlier, the Shanghai stockmarket had plunged dramatically, closing at its lowest since January 2009.
However, in 1990 an internal audit conducted in the wake of a shareholder's lawsuit revealed that Oracle had overstated its earnings, and the company's stock plunged dramatically.
According to a report in today's Moscow Times, the price for black market tickets has plunged dramatically – from a high of €2,000£1,60000) a few days ago to €500.
"They have sent someone to take care of you". The recruits nervously smoked cigarettes as the boat chugged past sheer, rocky cliffs that plunged dramatically into the still expanse of water.
Even the slow-dawning realisation that Lynch was less interested in a traditional crime story than in melding a Blue Velvet-style excavation of small-town America with a supernatural mystery did little to dim the fervour of true believers (although the show's ratings plunged dramatically, leading network ABC to pull the plug at the end of the second season).
After a tiny cough at the beginning of 2016, the stock market rose to new peaks, bringing NASDAQ to its highest price in history — even higher than before it plunged dramatically at the turn of the new millennium.
This could potentially cause the ivory markets to crash because prices would plunge dramatically.
Rugged mountains loom over fields the color of tennis balls, and cliffs plunge dramatically into Tanzanite-blue ocean.
Here, we breath in the scenery where to the East, a gorge plunges dramatically down and, far below to the West, the city goes about its business.
Not many members of India's elite, which is what she is, have a parent who's plunged so dramatically into the social abyss.
It also offers some reasons as to why voter turnout, even in newer and hard-won democracies like South Africa has plunged so dramatically - why bother if it will make no difference?
