Although the growth in Canada's population had slowed down by 1966 (the increase the first half of the 1960's was only nine percent), another large population wave was coming over the horizon.
主句：Another large population wave was coming over the horizon.
状语从句1：Although the growth in Canada's population had slowed down by 1966.
状语从句2：The increase the first half of the 1960's was only nine percent.
主句：Another large population wave[主语] was coming[谓语] over the horizon[状语].
状语从句1：The growth in Canada's population[主语] had slowed down[谓语] by 1966[状语].
状语从句2：The increase[主语] the first half of the 1960's[定语] was[系动词] only [状语] nine percent[表语].
1\.Although 与 but 不连用，与 yet/still/nevertheless 连用加强语气。
e.g. Although the weather was extremely cold, yet they worked with great enthusiasm.
e.g. Although he was ill, still he managed to look careful.
2\.Although 引导的让步从句有时省略了与主句相同的主语及其相应的 be 动词。
e.g. Although punctual himself, the professor was quite used
to students’being late for his lecture.
翻译：尽管教授本人很准时，但是对学生上他的课迟到已经很习惯了。（although 后省去he was）
3\. Although较为正式，语气比 though 重，常用于句首, 不可做副词使用。
e.g.She promised to phone. I heard nothing, though.(句末做副词时，只能用though，而不能用although)