The properties appraised and reviewed by Jonathan have all been located in the New York City borough of Manhattan. Jonathan has performed extensive assignments concerning mortgage origination, relocation, divorce, foreclosure, bankruptcy, asset valuation, share allocation, common area valuation, trust and estate matters and has been admitted as an expert witness in four different venues.

Jonathan has been a frequent featured speaker at both local and national appraiser and real estate related conferences, industry panels and trade groups. He has served on advisory panels for the Employee Relocation Council concerning co-op, appraisal and technology issues, is an ongoing taskforce panel member for Fannie Mae on co-op matters, is a member of the Mayor's Economic Advisory Panel for the New York City Office of Management and Budget and is a member of the New York City Council Finance Committee Economic Advisory Board.

He has participated in, or his statistics has been used within, research projects with a number of government agencies, consulting groups, and academic institutions, including New York University, Princeton University, Harvard University, Columbia University and Baruch College. His firm provides Manhattan market statistical content to New York Times Digital, the on-line entity of the New York Times Company. Jonathan regularly authors articles on valuation issues, techniques and market trends.

In 2005, Jonathan built and launched two widely read real estate blogs: Matrix: Interpreting the Real Estate Economy and Soapbox: Appraisal Ethics, Ideas and Industry Issues. He is currently the webmaster for both of these sites.

Since 1994, Jonathan has authored several widely read reports on the Manhattan real estate market for Prudential Douglas Elliman: The Manhattan Market Report (10-year analysis), The Manhattan Market Overview (quarterly) and The Manhattan Townhouse Report (10-year analysis). The reports are the first to cover the entire island of Manhattan and the only major studies that are independently prepared, making them the "reports of record." They are widely used by local, regional and national media as well as national and local lending institutions, various government agencies, the Federal Reserve, New York City Office of Management and Budget and the Internal Revenue Service. The reports have an annualized distribution in both print and internet downloads of more than 300,000 copies.