What is the change in payroll and incentive compensation between 2018 and 2019?
{"Payroll and incentive compensation": {"2019": 3009, "2018": 1937}, "Current portion of operating lease liabilities     ": {"2019": 285, "2018": "-"}, "Real estate taxes": {"2019": 398, "2018": 398}, "Other": {"2019": 395, "2018": 442}, "Total accrued expenses": {"2019": 4087, "2018": 2777}}
payroll_and_incentive_compensation_2019 = df["Payroll and incentive compensation"]["2019"]
payroll_and_incentive_compensation_2018 = df["Payroll and incentive compensation"]["2018"]
answer = payroll_and_incentive_compensation_2019 - payroll_and_incentive_compensation_2018