Note 11 - Employee Benefits

12 Months Ended

Dec. 31, 2013

Disclosure Text Block Supplement [Abstract]

Compensation and Employee Benefit Plans [Text Block]

11.    Employee Benefits

Stock Incentive Plans - Under our 2005 Stock Incentive Plan (the “2005 Plan”), all of our employees and any subsidiary employees, as well as all of our non-employee directors, may be granted stock-based awards, including non-statutory stock options and performance unit awards. Stock options expire within 7 or 10 years after the date of grant and the exercise price must be at least the fair market value of our common stock on the date of grant. Stock options issued to non-employee directors upon their annual re-election to our Board of Directors are generally exercisable at the date of grant. Stock options issued to employees are generally exercisable beginning one year from the date of grant in cumulative amounts of 20% per year. Performance unit awards are subject to vesting requirements over a five-year period, primarily based on our earnings growth. Options exercised and performance unit award shares issued represent newly issued shares. The maximum number of shares of common stock available for issuance under the 2005 Plan is 2.85 million shares. As of December 31, 2013, there were 1,015,759 shares reserved for issuance under options outstanding and 197,163 shares reserved for issuance under outstanding performance unit awards under the 2005 Plan.

We account for share-based payment arrangements in accordance with FASB ASC 718, Compensation-Stock Compensation, which requires all share-based payments to employees and non-employee directors, including grants of stock options and performance unit awards, to be recognized in the income statement based on their fair values at the date of grant.

We use the Black-Scholes option pricing model to calculate the grant-date fair value of option awards. The fair value of service-based option awards granted was estimated as of the date of grant using the following weighted average assumptions:

	2013			2012			2011
Expected option life in years(1)		6.1			6.1			6.3
Expected stock price volatility percentage(2)		33	%		37	%		39	%
Risk-free interest rate percentage(3)		1.5	%		1.1	%		2.4	%
Expected dividend yield(4)		0.51	%		0.49	%		0.38	%
Fair value as of the date of grant	$	5.46		$	4.81		$	5.69

(1)     Expected option life – We use historical employee exercise and option expiration data to estimate the expected life assumption for the Black-Scholes grant-date valuation. We believe that this historical data is currently the best estimate of the expected term of a new option. We use a weighted-average expected life for all awards.

(2)     Expected stock price volatility – We use our stock’s historical volatility for the same period of time as the expected life. We have no reason to believe that its future volatility will differ from the past.

(3)     Risk-free interest rate – The rate is based on the U.S. Treasury yield curve in effect at the time of the grant for the same period of time as the expected life.

(4)            Expected dividend yield – The calculation is based on the total expected annual dividend payout divided by the average stock price.

 We use the straight-line attribution method to recognize expense for all service-based option awards with graded vesting. Service-based option awards become immediately exercisable in full in the event of retirement, death or disability and upon a change in control with respect to all options that have been outstanding for at least six months. To be eligible for retirement, an employee must reach age 65.

Compensation costs associated with service-based option awards are recognized, net of an estimated forfeiture rate, over the requisite service period, which is the period between the grant date and the earlier of the award’s stated vesting term or the date the employee is eligible for retirement. We immediately recognize the entire amount of share-based compensation cost for employees that are eligible for retirement at the date of grant. For awards granted to employees approaching retirement eligibility, we recognize compensation cost on a straight-line basis over the period from the grant date through the retirement eligibility date. Share-based compensation expense for employees who are not retirement eligible is recognized on a straight-line basis over the stated vesting period of the award.

In August 2010, we granted 95,100 performance unit awards under our 2005 Stock Incentive Plan to certain employees. This was our first grant of such awards. As of December 31, 2010 and each December 31^st thereafter through December 31, 2014, each award vests and becomes the right to receive a number of shares of common stock equal to a total vesting percentage multiplied by the number of units subject to such award. The total vesting percentage for each of the five years is equal to the sum of a performance vesting percentage, which is the percentage increase, if any, in our diluted net income per share for the year being measured over the prior year, and a service vesting percentage of five percentage points. The goal of the awards is to incentivize the certain employees to increase our earnings an average of 15 percent per year over five years, which, when combined with the five percent per year service-based component, would result in full vesting over five years. The performance vesting percentage could be achieved earlier than in five years if annual earnings growth exceeds the average of fifteen percent, or not fully achieved if the annual earnings growth averages less than fifteen percent over the five-year period. All payments will be made in shares of our common stock. One half of the vested performance units will be paid to the employees immediately upon vesting, with the other half being credited to the employees’ accounts within the Marten Transport, Ltd. Deferred Compensation Plan, which restricts the sale of vested shares to the later of each employee’s termination of employment or attainment of age 62.

In August 2011, we also granted 62,400 performance unit awards with similar terms to the awards granted in 2010, and which vest from December 31, 2011 through December 31, 2015.

In May 2012, we also granted 59,250 performance unit awards with similar terms to the awards granted in 2010 and 2011, and which vest from December 31, 2012 through December 31, 2016.

In May 2013, we also granted 62,550 performance unit awards with similar terms to the awards granted in 2010 through 2012, and which vest from December 31, 2013 through December 31, 2017.

The fair value of each performance unit is based on the closing market price on the date of grant. We recognize compensation expense for these awards based on the estimated number of units probable of achieving the vesting requirements of the awards, net of an estimated forfeiture rate.

The amount of share-based compensation recognized during a period is based on the value of the portion of the awards that are ultimately expected to vest. Forfeitures are estimated at the time of grant and revised, if necessary, in subsequent periods if actual forfeitures differ from those estimates. We currently expect, based on an analysis of our historical forfeitures and known forfeitures on existing awards, that approximately 1.25% of unvested outstanding awards will be forfeited each year. This analysis will be re-evaluated quarterly and the forfeiture rate will be adjusted as necessary. Ultimately, the actual expense recognized over the vesting period will only be for those shares that vest.

 Total share-based compensation expense recorded in 2013 was $1.1 million ($672,000 net of income tax benefit, $0.02 of earnings per basic and diluted share), in 2012 was $1.2 million ($759,000 net of income tax benefit, $0.023 of earnings per basic and diluted share) and in 2011 was $1.3 million ($837,000 net of income tax benefit, $0.025 of earnings per basic and diluted share). All share-based compensation expense was recorded in salaries, wages and benefits expense.

The benefits of tax deductions in excess of recognized compensation costs (excess tax benefits) are recorded as a financing cash inflow rather than a deduction of taxes paid in operating cash flows. In 2013, 2012 and 2011, there was $165,000, $336,000 and $142,000, respectively, of excess tax benefits recognized resulting from exercises of options.

As of December 31, 2013, there was a total of $1.6 million of unrecognized compensation expense related to unvested service-based option awards, which is expected to be recognized over a weighted-average period of 3.5 years, and $1.4 million of unrecognized compensation expense related to unvested performance unit awards, which will be recorded based on the estimated number of units probable of achieving the vesting requirements of the awards through 2017.

Option activity in 2013 was as follows:

				Weighted
				Average
	Shares			Exercise Price
Outstanding at December 31, 2012		995,046		$	13.01
Granted		174,625			16.76
Exercised		(120,762	)		9.36
Forfeited		(33,150	)		13.83
Outstanding at December 31, 2013		1,015,759		$	14.07
Exercisable at December 31, 2013		684,309		$	13.48

The 1,015,759 shares outstanding as of December 31, 2013 have a weighted average remaining contractual life of 4 years and an aggregate intrinsic value based on our closing stock price on December 31, 2013 for in-the-money options of $6.2 million. The 684,309 shares exercisable as of the same date have a weighted average remaining contractual life of 3.3 years and an aggregate intrinsic value similarly calculated of $4.6 million.

The fair value of options granted in 2013, 2012 and 2011 was $953,000, $695,000 and $350,000, respectively, for service-based options. The total intrinsic value of options exercised in 2013, 2012 and 2011 was $915,000, $1.4 million and $442,000, respectively. Intrinsic value is the difference between the fair value of the acquired shares at the date of exercise and the exercise price, multiplied by the number of options exercised. Proceeds received from option exercises in 2013, 2012 and 2011 were $1.1 million, $968,000 and $137,000, respectively.

Nonvested option awards as of December 31, 2013 and changes during 2013 were as follows:

						Weighted
						Average
				Weighted		Remaining
				Average		Contractual
				Grant Date		Life
	Shares			Fair Value		(in Years)
Service-based options:
Nonvested at December 31, 2012		297,330		$	5.21		5.2
Granted		174,625			5.46		7.0
Vested		(120,405	)		5.28		4.5
Forfeited		(20,100	)		5.46		4.0
Nonvested at December 31, 2013		331,450		$	5.30		5.5

The total fair value of options which vested during 2013, 2012 and 2011 was $636,000, $751,000 and $856,000, respectively.

The following table summarizes our nonvested performance unit award activity in 2013:

				Weighted Average
				Grant Date
	Shares			Fair Value
Nonvested at December 31, 2012		114,819		$	13.49
Granted		62,550			14.29
Vested		(35,894	) (1)		13.67
Forfeited		(23,943	)		13.74
Nonvested at December 31, 2013		117,532		$	13.81

(1)           This number of performance unit award shares vested based on our financial performance in 2013 and was distributed or credited to the Marten Transport, Ltd. Deferred Compensation Plan in March 2014. The fair value of unit award shares that vested in 2013 was $491,000.

Retirement Savings Plan - We sponsor a defined contribution retirement savings plan under Section 401(k) of the Internal Revenue Code. Employees are eligible for the plan after three months of service. Participants are able to contribute up to the limit set by law, which in 2013 was $17,500 for participants less than age 50 and $23,000 for participants age 50 and above. We contribute 35% of each participant’s contribution, up to a total of 6% contributed. Our contribution vests at the rate of 20% per year for the first through fifth years of service. In addition, we may make elective contributions as determined by the Board of Directors. No elective contributions were made in 2013, 2012 or 2011. Total expense recorded for the plan was $1.4 million in 2013, $909,000 in 2012 and $803,000 in 2011.

Stock Purchase Plans - An Employee Stock Purchase Plan and an Independent Contractor Stock Purchase Plan are sponsored to encourage employee and independent contractor ownership of our common stock. Eligible participants specify the amount of regular payroll or contract payment deductions and voluntary cash contributions that are used to purchase shares of our common stock. The purchases are made at the market price on the open market. We pay the broker’s commissions and administrative charges for purchases of common stock under the plans.