Deme B maintained a population of 9931 until there was a shift 983.1 generations ago that changed its numbers to 1936, a figure that has remained the same since.
time_units: generations
demes:
  - name: B
    start_time: .inf
    epochs:
      - start_size: 9931
        end_time: 983.1
      - start_size: 1936
        end_time: 0