I suspect you are referring to the thread at Study Conducted by Stanford Suggests Essay Content Correlates more Strongly with Household Income than SAT - #8 by Data10 . This study did not consider the admission readers’ ratings of applicants or whether the applicant wrote a quality essay. It only looked at whether the essays had certain key words groupings that were correlated with SES such as China, travel, and business economics. For example, kids who write about traveling to China in their essays are more likely to be high income than average, so a computer seeing an essay with keywords related to China and travel might be able to successfully guess the applicant was high income. However, this does not mean that kids who write about traveling to China in their essays are more likely to receive a high essay rating or more likely be admitted. A quote from the thread is below:
Note that the study did not evaluate the admission readers’ raters of the essay or which students had the best essays from an admission stand point. Instead they estimated the essay topic by using a computer program that counted frequency of key words within the essay, and found that choosing certain essay topics (as estimated by the key word count) was correlated with income and SAT score.
For example, wring essays about “seeking answers” had a high 0.57 correlation with SAT score. “Seeking answers” topic was estimated by a high frequency of using key words like “question, book, like, research, read, answer, ask” within the essay. Similarly writing essays about “tutoring groups” shows a strong negative correlation with SAT score. Kids with higher SAT scores were less likely to write essays about “tutoring groups.”
The correlations between certain estimated essay topics and SAT score seem quite substantial, while the correlations between estimated essay topics and income seem much lower. The essay topic that was most correlated with income seems to be writing about China, as estimated by high frequency of the key words “chines, studi, student, also, time, china, school.” I’m not sure how much some of these key words have to do with China, but I don’t doubt that writing essays about China would be correlated with income – both due to higher income among Chinese international students (UC sample group) and among students who travel to China. However, this does not mean that the kids who wrote essays about China or traveling had better essays from an admission stand point-- only that they were more likely to have higher income.