核心问题
During that time, 174 babies were born in the world. Maybe you think that isn't many. 《中学英语 1 + 1 · 高一英语同步讲解与测试》(上)(中国青年出版社, p.83)说：“many 和 few、a few 在句中可作定语、主语，但不能作表语。如只能说 I have many/few books. 而不能说 My books are many/few.” 请问 many 和 few 真的不能作表语吗？上面的 that isn't many 是否用错？
词典解答
CGEL的编著者R.Quirk等人在该书的索引中列出了many的predicative use(many的表语用法)词条,并在§5.23和§6.53两节中明确指出：
“many 和 few 在正式语体中还能用作表语: His faults were many/few. (他的缺点很多/很少。)”
“many 和 few 一样, 在正式语体中可以用作表语: His sins were many, and friends were few. (他的罪恶很多, 而他的朋友却很少。)”