<p>For many universities that require you to choose a major it can make a difference but the difference of significance is usually in colleges at the university. For example the engineering college at a university very often has a higher middle 50% range for those admitted than liberal arts & sciences or the university as a whole. That is also often true as to a business college at the university. The colleges within the university can also differ as to admission rate, e.g., the LAS college might usually admit 30% of the applicants but business may be only 25%. If econ is in the arts & sciences college at the universities to which you are applying then it won’t make much of a difference between it and undeclared. If econ is in the business college at the university to which you are applying then you need to consider that you might need higher stats than what you see as the middle 50% range published for the university as a whole and the business college’s admission rate may be soemwhat lower than the university as a whoile. And if allowed to declare a major and a second choice you can usually make undeclared that second choice but that depends on the particular university.</p>