Introduction. Beta-blockers, also known as beta-adrenoceptor blocking agents, are medications used to treat conditions such as angina, heart failure and high blood pressure. They decrease the activity of the heart by blocking the action of hormones like adrenaline.
1 The concept of âdemographic changeâ describes a populationâs age structure adjusting to. changes in living conditions. Consequently, changes in thcomposition of a societyâe s age. structure are the result of social shifts. (. 2  cf. . 3  theory of first and second demographic transition.
1 The United States added just 2.3 million people from 2010 to 2011, compared with 2.9 million from 2005 to 2006, just five years earlier. The decline in U.S. population growth is likely due to a confluence of factors: lower levels of immigration, population aging, and declining fertility rates.A drop in net immigration to the United States is a key factor in the country's declining population growth rate.Around the turn of the millennium, the Census Bureau was estimating net international migration at about 1.4 million per year.he recent decline in immigration has also accelerated population aging in the United States. Most immigrants are working-age adults, and many start families after they arrive in the U.S., creating an immigrant youth bulge.