Real estate economists remain optimistic that the industry will continue to grow through 2019, but certain market conditions have them tempering their forecasts.

That is according to the Urban Land Institute's spring 2017 real estate consensus forecast. The forecast, based on a survey of 53 economists and analysts from 39 global CRE firms, indicated that while industry fundamentals remain sound, a few factors have led them to be more cautious when predicting future growth.

That growth, incidentally, is expected to lead to a decline in transaction volume from 2015's high-water mark of $547B. The ULI forecast predicts total transaction volume will fall 8% from last year, to $450B. Economists believe that number will hold steady next year before dropping further to $430B by 2019.

Two main indicators of the slightly softening market include: a packed construction pipeline nationally in the office, multifamily and retail sectors and future interest rate hikes. The survey predicts total return rates on institutional-grade assets to top 7% this year before softening further to 6% the next two years.

The forecast stresses that this is not a sign that the industry is reaching the end of existing runway. Fundamentals such as rent spreads and vacancy rates continue to perform strongly across multiple sectors and are expected to continue moving forward. The exception is in apartment vacancies, which is expected to increase to 5.2% nationally this year, coupled with a flood of new product entering major markets.