WASHINGTON (CNS) -- A report from the Center for Migration Studies of New York said the population of immigrants living in the United States without documents has declined 10% in eight years.

In 2018, the center said, the total "U.S. undocumented population" was estimated to be 10.6 million, a drop of 1.2 million since 2010. The figures show a steady downward pattern as immigration from Mexico to the U.S. has decreased and Mexican nationals have returned home, the report said.

The report "Reverse Migration to Mexico Led to U.S. Undocumented Population Decline: 2010 to 2018," released Feb. 28, says that from 2010 until 2018, a total of 2.6 million Mexican nationals "left the U.S. undocumented population" and 45% of those "left voluntarily."

The document says it shows that "improving social and economic conditions in sending countries would not only reduce pressure at the border but also likely cause a large decline in the undocumented population."

It mirrors the policy position and recommendations of the U.S. Conference of Catholic Bishops, which has said that improving "sustainable and equitable development in sending nations, especially Mexico and the countries of Central America" can help address the root causes of the present immigration crisis in the U.S., "so that migrants can remain in their homelands and support their families in dignity."

The report, based on data collected in the U.S. Census Bureau's American Community Survey, says that when it comes to immigration from Central America, particularly the countries of El Salvador, Guatemala and Honduras, the number of nationals from those countries entering without documentation "has been constant, rather than increasing since 2014," and that an increase in apprehensions of those nationals has not made a difference in the numbers of those who attempt to enter.

The report also shows that two-thirds of the total of those who have entered the country without documentation since 2010 have entered with a temporary visa and simply not returned when they were supposed to, while just one-third "entered illegally across the border."

And of those who remain in the country without documents, who numbered 10.6 million in 2018, "about 5.7 million (54%) entered across the border, and 4.9 million (46%) entered with a temporary visa and overstayed (it)," the report says.

Despite the decline, nationals from Mexico remain at the top of the list of the top 10 countries with the most number of foreign nationals without documentation in the U.S. followed by El Salvador, India, Guatemala, Honduras, China, Philippines, Dominican Republic, Venezuela and Korea.