t = 10;
keys = {"Year","x1","x2","x3"};
years = Range[t];
x1values = RandomReal[10, t]; (* your Array[S, t] *)
x2values = RandomInteger[1000, t]; (* your Array[R, t] *)
x3values = RandomWord["Noun", t];

data = Dataset[AssociationThread[keys -> #]&/@
    Transpose[{years, x1values, x2values, x3values}]]

t = 10;
keys = {"Year","x1","x2","x3"};
years = Range[t];
x1values = RandomReal[10, t]; (* your Array[S, t] *)
x2values = RandomInteger[1000, t]; (* your Array[R, t] *)
x3values = RandomWord["Noun", t];

data = Dataset[AssociationThread[keys -> #]&/@
    Transpose[{years, x1values, x2values, x3values}]]

ds = Dataset[AssociationThread[{"Year", "x1", "x2", "x3", "x4"} -> #] & /@ 
  Transpose[{Range[10], Array[S, t], Array[R, t], Array[Y, t], Array[S[#]/R[#] &, t]}]]