"'Defining the Universe' is Essential When Writing About Research Data" (Gramlich) The link address is: http://www.pewresearch.org/fact-tank/2018/10/18/defining-the-universe-is-essential-when-writing-about-survey-data/?utm_source=Pew+Research+Center&utm_campaign=0f0d19d9a6-EMAIL_CAMPAIGN_2018_10_24_02_55&utm_medium=email&utm_term=0_3e953b9b70-0f0d19d9a6-400573021