正确语法不应该用"are",'has' 应该是 ‘have',因为 'people' 是负数 'that' 应该在 ‘found' 后面,’idle‘后面不需要加 'that'或插入 'so...that...'形式.'they'd' 是不正规的缩写,的正确写法是 'they would'.
正确的句子应该是：
"people have found that more than half of adults are so idle they would catch the lift rather than climb two flights of stairs."