The phrase "exports account for half our income" can be restated in various ways to convey the same message. Some synonyms for the word "exports" are "foreign sales", "overseas trade", and "international commerce". Similarly, "account for" could be replaced with "make up", "constitute", or "represent". "Half our income" can be rephrased as "50% of our revenue", "a significant portion of our earnings", or "a major source of our profits". Overall, there are multiple ways to convey the idea that a significant proportion of a company's income is derived from sales abroad.