for limiting annual immigration to between 30,000 and 300,000. The organization, Population-Environment Balance (PEB), issued an "Immigration Moratorium Action Plan" calling for a "non-piercable" cap of 100,000 persons annually, which would be a 95% cut from current levels. There are also some who support a moratorium on immigration. The Diversity Alliance for a Sustainable America claims that 43% of Californians polled said that a 3-year moratorium on immigration would be beneficial to the state (compared to 40% who said it would be futile). The America First Party calls for a ten-year moratorium, with only spouses and children of citizens allowed in. Other advocates for moratoriums include the Reform Party and 2004 Constitution Party presidential candidate Michael Peroutka. The Carrying Capacity Network (CCN) and Population-Environment Balance (now defunct), two groups that both operate out of the same Washington, D.C. address, issue frequent statements that advocating for the numbers recommended by the Jordan Commission, 700,000 annually, is "counter-productive". In a National Alert, the CCN warned that organizations supporting numbers higher than 300,000 undercut the movement, and they specifically criticize the Federation for American Immigration Reform and NumbersUSA. Some groups not connected to the immigration reduction movement nonetheless support a reduction to legal immigration levels of around 500,000 to 600,000. In their 1997 book, Misplaced Blame, Alan Durning and Christopher Crowther of Northwest Environment Watch write that illegal immigration gets too much attention, and identify five main sources of population growth, including lack of access to family planning as well as a misguided legal immigration policy, and subsidies to domestic migration. They readily admit that immigration should be reduced by an unspecified amount, but they also show concern for the rights of existing residents. Proposed methods to reduce illegal immigration Border barriers The United States-Mexico barrier has been partially constructed to reduce the flow of unauthorized migrants into the United States. The Trump wall is a colloquial name for a proposed expansion of the Mexico–United States barrier during the presidency of Donald Trump. Attrition through enforcement Pro-enforcement U.S. think tanks such as the Center for Immigration Studies have supported an "attrition through enforcement" doctrine. The aim here is to, as that organization states, "Shrink the illegal population through consistent, across-the-board enforcement of the immigration law. By deterring the settlement of new illegals, by increasing deportations to the extent possible, and, most importantly, by increasing the number of illegals already here who give up