百思一解
每個人都在尋求認同，在幾十億的人海裏。每個人都在尋求答案，在無窮多的可能中。
正文
前不久發了一篇“美國25年的人口結構變化趨勢”的短文，引起了網友的興趣，我們在那篇博文的跟帖裏交換了很多看法。很多看法與我相左，但有相當多很有深度和代表性的問題。應網友請求，把我們的討論和我對移民政策的看法整理一下，和大家分享。無關對錯，隻是分享不同意見。
因為在“美國25年的人口結構變化趨勢”並未太觸及移民政策，這裏我先簡單概括一下我對移民政策的看法：
- 美國需要移民，移民對美國經濟的作用不可代替。
- 美國需要合法移民，不是非法移民。
- 非法移民多屬於低技能移民，對社會回報低。哪怕合法化以後仍是如此。
- 低工資非法移民勞動力會進一步擠占美國低端就業市場。
- 非法狀態無法管理，有很大安全漏洞，也容易繁衍出新的貧民窟。
- 非法移民帶來的社會問題，引起的仇恨也會影響合法移民在這個社會的正常生活。
- 因此美國必須要有效的手段降低非法移民，增加合法移民。
- 川普更有魄力和意願去解決這個問題。
由於網友提出的議題太多（大約有十個左右），不可能一次寫完，我會分幾次寫出來。
先來討論一個比較尖銳的問題：非法移民是否帶來安全問題。
[網友] Undocumented aliens are less likely to commit crime than native-born Americans.
[虎嘯山林] 網友引證的數據表明非法移民的犯罪率低於平均犯罪率。這確實可以理解，剛非法進入一個國家，多數人為了避免被當局發現而被遣返，行事會非常小心低調。但問題這些人是否需要合法化。合法化後恐怕就沒那麽多顧忌了。根據監獄的統計數據，西裔進監獄的概率2倍於白人，更不用說亞裔，不過確實比非裔低：
| Race/Ethnicity | % of US population | % of U.S. incarcerated population | National incarceration rate (per 100,000) |
| 64% | 39% | 450 per 100,000 | |
| Hispanic | 16% | 19% | 831 per 100,000 |
| Black | 13% | 40% | 2,306 per 100,000 |
即便如此，非法移民引進的極端犯罪可並非可以忽略的小事 （http://www.breitbart.com/big-journalism/2015/08/08/illegal-alien-crime-accounts-for-over-30-of-murders-in-some-states/）：
- Between 2008 and 2014, 40% of all murder convictions in Florida were criminal aliens. In New York it was 34% and Arizona 17.8%.
- During those years, criminal aliens accounted for 38% of all murder convictions in the five states of California, Texas, Arizona, Florida and New York, while illegal aliens constitute only 5.6% of the total population in those states.
這五個州38%的謀殺出自非法移民，包括俺住的加州！您說俺不應該擔心嗎？不管為自己還是我們的後代？
（待續）
The Mythical Connection Between Immigrants and Crime
Wall Street Journal
...numerous studies going back more than a century have shown that immigrants—regardless of nationality or legal status—are less likely than the native population to commit violent crimes or to be incarcerated. A new report from the Immigration Policy Center notes that while the illegal immigrant population in the U.S. more than tripled between 1990 and 2013 to more than 11.2 million, “FBI data indicate that the violent crime rate declined 48%—which included falling rates of aggravated assault, robbery, rape, and murder. Likewise, the property crime rate fell 41%, including declining rates of motor vehicle theft, larceny/robbery, and burglary.”
A separate IPC paper from 2007 explains that this is not a function of well-behaved high-skilled immigrants from India and China offsetting misdeeds of Latin American newcomers. The data show that “for every ethnic group without exception, incarceration rates among young men are lowest for immigrants,” according to the report. “This holds true especially for the Mexicans, Salvadorans, and Guatemalans who make up the bulk of the undocumented population.”
It also holds true in states with large populations of illegal residents. A 2008 report by the Public Policy Institute of California found that immigrants are underrepresented in the prison system. “The incarceration rate for foreign-born adults is 297 per 100,000 in the population, compared [with] 813 per 100,000 for U.S.-born adults,” the study concludes. “The foreign-born, who make up roughly 35% of California’s adult population, constitute 17% of the state prison population.”
High-profile incidents, like the recent arrest of a Mexican national in the horrific shooting death of a young woman in San Francisco, can give the impression that immigrants are more likely to commit violent crimes. But the alleged killer is no more representative of Mexican immigrants than Dylann Roof is representative of white people.
...In a 2005 paper, the Federal Reserve Bank of Chicago reported that more recently arrived immigrants are even less crime-prone than their predecessors. In 1980 the incarceration rate of foreign nationals was about one percentage point below natives. A decade later that had fallen to a little more than a percentage point, and by 2000 it was almost three percentage points lower.
See http://www.wsj.com/articles/the-mythical-connection-between-immigrants-and-crime-1436916798
即便如此，非法移民引進的極端犯罪可並非可以忽略的小事
I am afraid the source of this information is incorrect. An independent fact checking site had reviewed these numbers and explained that these statistics were wrong. Please see: "Tom Tancredo muffs illegal immigrant murder stats." (Tom Tancredo is the author of the report you cited).
(1): Firstly:
The presentation’s author, James Simpson, told us he had emailed Breitbart about Tancredo’s use of his presentation. "(Tancredo) quoted the whole thing incorrectly," Simpson told PunditFact.
(2): And:
Tancredo used the wrong time period. He thought the baseline number was homicide convictions when it was actually all homicides. Most important of all, he took the presentation he relied on at face value and ignored the hard numbers available from the Texas Department of Public Safety.
And while Tancredo might not have known it, the researcher whose work he used himself has questions about the underlying data he used. We have hard data from Texas that refutes the big and estimated numbers Tancredo used. Undocumented immigrants do commit murder, but perhaps only one-fifth as often as Tancredo said.
(3): As a result, the fact checking site concluded:
"We rate the claim False."
See http://www.politifact.com/punditfact/statements/2015/aug/17/tom-tancredo/tancredo-muffs-illegal-immigrant-murder-stats/
P.S.: This is the thing about Breitbart -- it has consistently misquoted information to spin things its way. I would caution you about the reliability of it as a source.