"markedly weaker" is a correct and usable phrase in written English.
It means significantly or noticeably weaker. You can use this phrase to describe a significant decrease in strength, ability, or quality in a sentence. Here is an example: "After the injury, his left arm was markedly weaker than his right, making it difficult for him to perform simple tasks like lifting or writing."
And in constituencies where Ukip got a high share of the vote, the Tory to Labour swing was markedly weaker.
Even then, the past three recoveries have been markedly weaker than those that came before.
Equities also fell after the Bank of England governor, Mervyn King, said Britain faced a "markedly weaker" outlook for the economy as Europe's crisis threatened global growth.
In comparison, the economic significance of order flow imbalance is markedly weaker.
Brazil's outlook is also markedly weaker, due to a lack of confidence among businesses and consumers.
Investors, business owners and ordinary Argentines grew more nervous, with the peso already markedly weaker on the black market.
Similarly, the Retreat strategy has a markedly weak asset performance for Land Values and Goods and Services as a function of the shift in greenspace land use.
This paper shows that in active orogens where markedly weak and markedly strong rocks are juxtaposed along contacts that parallel regional structures, relatively high topography can form where strain is localized in the weak rock.
James Paulsen of Norwest Investment Management, which is based in Minneapolis, Minnesota, points out that sales growth has been markedly weak in this recovery – only about 5% annually in this decade, compared with about 7% or more going back to the 1960s.
S&P futures are markedly lower, indicating a weak opening when trading gets under way in New York at 9 30 AM EST.
The signals of demographic expansions or contractions in lineages A and C were weak, with markedly smaller Fu's Fs absolute values which were generally not statistically significant, and estimations of g with 95% confidence intervals that overlap zero (Table 2).
