time series forecasting with 5 input variables

Hello, I'm pretty new to time series analysis, so am wondering if this is possible.

I have the following time series which have 5 variables (A,B,C,D,E) for 37 years (or see the attached). These 5 variables were computed with two constraints which are sum-to-one and non-negativity. What I want to do is forecasting values of these 5 variables for 38th year using some kind of time series analysis or whatever. The problem is I don't see any trends or significant relationships in these data. If you have any suggestions please let me know. Thank you!