"drastically decline" is a correct and usable phrase in written English.
It is used to describe a situation in which something decreases significantly. An example sentence would be: "When oil prices plummeted, many countries had to drastically decline their spending."
— World Bank predicts coal use will drastically decline in the next 30 years: "The model has been coal plus renewables, the model can be gas plus renewables.
Taro Aso, the new Japanese prime minister, said Monday that the government might expand an already announced $17.4 billion stimulus package, saying that exports, which have driven the economy in Japan for a decade, would "drastically decline".
Ministers say they want more effort to link flowering habitats across the countryside, from gardens to farms, especially given that pollinators are worth up to £430m a year yet have seen their population drastically decline.
The action is the result of free agency, the salary-cap system and the parity that has ensued, resulting in a cycle of teams who in any given season seem to rise from nowhere and teams who drastically decline with equal surprise.
Between the end of March, when new police training was started, and the end of October, the number of stops did drastically decline — a 28 percent decrease, to an average of 120,000 every three months in 2012 from about 166,000 for those same months in 2011.
KLIC bears are betting on the growth in semiconductors to not only slow, but drastically decline (based on expectations baked into the stock price).
As in other areas, activity drastically declined after ca. 300 cal BP (Supplementary Table S1).
Women and men are most fertile in their early 20s, while female fertility drastically declines after 35.
In truth, steel imports have been drastically declining since the glut caused by the Asian financial crisis.
But even in areas that never drastically declined, the image that infected the Bronx in the '80s has held on.
Even in the relatively recent past, the area of land over which these animals roamed has drastically declined.
