Originally, deme U had a population size of 9733, which reduced to 5373 around 6236.8 generations ago and has not changed since.
time_units: generations
demes:
  - name: U
    start_time: .inf
    epochs:
      - start_size: 9733
        end_time: 6236.8
      - start_size: 5373
        end_time: 0