“下降趋势”常见的英文表达有 "downward trend" 或 "declining trend"。
"downward trend"：强调趋势是向下的，使用较为普遍。
例句：The company has been experiencing a downward trend in sales over the past year.（过去一年，该公司的销售额一直呈下降趋势。）
"declining trend"：侧重于描述逐渐减少或衰落的趋势。
例句：There is a declining trend in the number of students choosing science majors.（选择理科专业的学生人数呈下降趋势。）