Under Matthei's tenure, the number of community land trusts increased from a dozen to more than 100 groups in 23 states, creating many hundreds of permanently affordable housing units, as well as commercial and public service facilities. With colleagues Matthei guided the development of 25 regional loan funds and organized the National Association of Community Development Loan Funds, later known as the National Community Capital Association. From 1985–1990, Matthei served as a founding Chairman of the Association and from 1983–1988 he served as a founding board member of the Social Investment Forum, the national professional association in the field of socially responsible investment. Matthei and his colleagues at the Institute for Community Economics also launched an effort in the early to mid-1980s to address many of the legal and operational questions about CLTs that were arising as banks, public officials and1 by an ecumenical association of churches and ministries created to prevent the displacement of low-income, African-American residents from their neighborhood.