The banking industry still hasn’t touched bottom in its years-long retreat from the mortgage servicing rights business. Banks and thrifts reported a total of $4.001 trillion of single-family mortgage servicing for other investors, most commonly mortgage-backed securities trusts, as of the end of March. That was down some $52.9 billion from the previous quarter, a 1.3 percent decline, according to a new analysis of call-report data by Inside Mortgage Trends ... [Includes one data chart]