Years Ended December 31,
2019
2018
2017
Federal income tax expense at statutory rates
$(11,061)
$(8,690)
$(10,892)
Effect of:
State income taxes, net of federal benefit
(2,973)
(2,665)
(2,244)
Impact of foreign operations
(11)
(146)
74
Non-deductible expenses
(592)
(1,274)
(1,350)
Federal tax rate change
—
—
(9,046)
Tax effect of TCJA from foreign earnings
(28)
(130)
(2,296)
Other
(581)
(645)
239
Changes in valuation allowance
92
835
273
Income tax expense
$(15,154)
$(12,715)
$(25,242)

text: 5. Income taxes: (Continued)
text: In the normal course of business the Company takes positions on its tax returns that may be challenged by taxing
authorities. The Company evaluates all uncertain tax positions to assess whether the position will more likely than not
be sustained upon examination. If the Company determines that the tax position is not more likely than not to be
sustained, the Company records a liability for the amount of the benefit that is not more likely than not to be realized
when the tax position is settled. The Company does not have a liability for uncertain tax positions at December 31,
2019 and does not expect that its liability for uncertain tax positions will materially increase during the twelve months
ended December 31, 2020, however, actual changes in the liability for uncertain tax positions could be different than
currently expected. If recognized, changes in the Company's total unrecognized tax benefits would impact the
Company's effective income tax rate.
In the normal course of business the Company takes positions on its tax returns that may be challenged by taxing authorities. The Company evaluates all uncertain tax positions to assess whether the position will more likely than not be sustained upon examination. If the Company determines that the tax position is not more likely than not to be sustained, the Company records a liability for the amount of the benefit that is not more likely than not to be realized when the tax position is settled. The Company does not have a liability for uncertain tax positions at December 31, 2019 and does not expect that its liability for uncertain tax positions will materially increase during the twelve months ended December 31, 2020, however, actual changes in the liability for uncertain tax positions could be different than currently expected. If recognized, changes in the Company's total unrecognized tax benefits would impact the Company's effective income tax rate. In the normal course of business the Company takes positions on its tax returns that may be challenged by taxing authorities. The Company evaluates all uncertain tax positions to assess whether the position will more likely than not be sustained upon examination. If the Company determines that the tax position is not more likely than not to be sustained, the Company records a liability for the amount of the benefit that is not more likely than not to be realized when the tax position is settled. The Company does not have a liability for uncertain tax positions at December 31, 2019 and does not expect that its liability for uncertain tax positions will materially increase during the twelve months ended December 31, 2020, however, actual changes in the liability for uncertain tax positions could be different than currently expected. If recognized, changes in the Company's total unrecognized tax benefits would impact the Company's effective income tax rate. In the normal course of business the Company takes positions on its tax returns that may be challenged by taxing authorities. The Company evaluates all uncertain tax positions to assess whether the position will more likely than not be sustained upon examination. If the Company determines that the tax position is not more likely than not to be sustained, the Company records a liability for the amount of the benefit that is not more likely than not to be realized when the tax position is settled. The Company does not have a liability for uncertain tax positions at December 31, 2019 and does not expect that its liability for uncertain tax positions will materially increase during the twelve months ended December 31, 2020, however, actual changes in the liability for uncertain tax positions could be different than currently expected. If recognized, changes in the Company's total unrecognized tax benefits would impact the Company's effective income tax rate.
text: The Company or one of its subsidiaries files income tax returns in the US federal jurisdiction and various state and foreign jurisdictions. The Company is subject to US federal tax and state tax examinations for years 2004 to 2019. The Company is subject to tax examinations in its foreign jurisdictions generally for years 2005 to 2019.
text: The following is a reconciliation of the Federal statutory income taxes to the amounts reported in the financial statements (in thousands).

Questions:
question: What are the respective federal income tax expense at statutory rates in 2017 and 2018?
answer: 10,892
8,690
scale: thousand
question: What are the respective federal income tax expense at statutory rates in 2018 and 2019?
answer: 8,690
11,061
scale: thousand
question: What are the respective state income taxes, net of federal benefit in 2017 and 2018?
answer: 2,244
2,665
scale: thousand
question: What is the average federal income tax expense at statutory rates in 2017 and 2018?
answer: 9791
derivation: (10,892 + 8,690)/2 
scale: thousand
question: What is the average federal income tax expense at statutory rates in 2018 and 2019?
answer: 9875.5
derivation: (8,690 + 11,061)/2 
scale: thousand
question: What is the average state income taxes, net of federal benefit in 2017 and 2018?
answer: 2454.5
derivation: (2,244 + 2,665)/2 
scale: thousand