"Inter-racial trust is relatively high in homogeneous South Dakota and relatively low in heterogeneous San Francisco or Los Angeles. The more ethnically diverse the people we live around, the less we trust them. […] the more we are brought into physical proximity with people of another race or ethnic background,the more we stick to ‘our own’ and the less we trust the ‘other"
“Diverse communities tend to be larger, more mobile, less egalitarian, more crime-ridden”
“Within experimental game settings such as prisoners-dilemma or ultimatum games, players who are more different from one another (regardless of whether or not they actually know one another) are more likely to defect (or ‘cheat’).”https://web.archive.org/web/20160205043520/https://www.msu.edu/~zpneal/publications/neal-diversitysoc.pdf
“Community psychologists are interested in creating contexts that promote both respect for diversity and sense of community. However, recent theoretical and empirical work has uncovered a community-diversity dialectic wherein the contextual conditions that foster respect for diversity often run in opposition to those that foster sense of community. […] integration provides opportunities for intergroup contact that are necessary to promote respect for diversity but may prevent the formation of dense inter-personal networks that are necessary to promote sense of community.”https://link.springer.com/article/10.1007/s11205-015-0863-3
“In line with the majority of previous studies, we find negative effects of statistical ethnic diversity on each of our five measures of neighborhood social cohesion: trust, collective efficacy, connectedness, reported social problems, and overall satisfaction with neighborhood life. With few
exceptions these effects are statistically significant in all three countries and apply to natives and persons of immigrant origin very much alike.”https://www.jstor.org/stable/425106?seq=1#page_scan_tab_contents
“The more ethnic groups in a state, the more likely it will have a high rate of guerrilla and revolutionary warfare. And the more religious groups in a society, the more intense the general violence. This is largely moderated by the size of a state. Thus, the larger and older (counting from 1932) a state in addition to the more religious groups, the more the general violence.”https://www.scirp.org/reference/ReferencesPapers.aspx?ReferenceID=1251240
“Ethnic heterogeneity [diversity] explains 55% of the variation in the scale of ethnic conflicts, and the results of regression analysis disclose that the same relationship more or less applies to all 187 countries. These results led to the conclusion that ethnic nepotism is the common cross-cultural background factor which supports the persistence of ethnic conflicts in the world as long as there are ethnically divided societies.”http://onlinelibrary.wiley.com/doi/10.1111/j.1465-7287.2010.00215.x/abstract
“Using data from U.S. states, I investigate the relationship between ethnic diversity and trust. I find a negative relationship between ethnic polarization and trust […] The main channel through which ethnic diversity is hypothesized to affect trust is social conflict.”http://www.ifs.org.uk/uploads/publications/wps/WP201530.pdf
“We find that a small minority group will adopt majority cultural practices and integrate. In contrast, minority groups above a certain critical mass, may retain diverse practices and may also segregate from the majority. The size of this critical mass depends on the cultural distance between groups, the importance of culture in day to day life, and the costs of forming a social tie.http://fivethirtyeight.com/features/the-most-diverse-cities-are-often-the-most-segregated/
“It is all too common to live in a city with a wide variety of ethnic and racial groups — including Chicago, New York, and Baltimore — and yet remain isolated from those groups in a racially homogenous neighborhood. […] the exceptions are cities like Sacramento that have large Hispanic or Asian populations. Cities with substantial black populations tend to be highly segregated. Of the top 100 U.S. cities by population, 35 are at least one-quarter black, and only 6 of those cities have positive integration scores.”https://dash.harvard.edu/bitstream/handle/1/4553003/alesinassrn_fractionalization.pdf?sequence=2
“We concluded that ethnic and linguistic diversity fractionalization variables, but not religious ones, are likely to be important determinants of economic success, both in terms of output (GDP growth), the quality of policies, and the quality of institutions.”https://dash.harvard.edu/bitstream/handle/1/4553005/alesinassrn_ethnicdiversity.pdf?sequence=2
Diversity is negatively associated with economic growth, even after controlling for wealth over time.https://ils.unc.edu/courses/2013_spring/inls285_001/materials/WIlliams.OReilly.1996.Diversity&demography.pdf
A review of 80 studies spanning 40 years concludes that diversity impedes group functioning and is most likely to cause negative effects.
“Simply having more diversity in a group is no guarantee that the group will make better decisions or function effctively. […] empirical evidence suggests that diversity is most likely to impede group functioning. […] diversity by itself is more likely to have a negative than positive effects on group performance. […] There is substantial evidence from both laboratory and field studies conducted over the past four decades that variations in group composition can have important effects on group functioning. These studies show that increased diversity, especially in terms of age, tenure, and ethnicity, typically have negative effects on social integration, communication, and conflict.”