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Equity Incentive Plans and Stock Based Compensation (Tables)
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12 Months Ended |
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Dec. 31, 2013
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| Disclosure Of Compensation Related Costs Sharebased Payments [Abstract] |
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| Stock Option Activity Under Equity Incentive Plan |
Activity under the 2004 Plan is set forth below:
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Shares
Available
for Grant |
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Outstanding Options |
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Weighted
Average
Exercise
Price |
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Number of
Shares |
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Exercise
Price |
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Balances, December 31, 2010
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765,848 |
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2,745,718 |
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$ |
0.42–3.18 |
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$ |
1.36 |
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Additional shares reserved
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1,250,000 |
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— |
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Options granted
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(1,196,500 |
) |
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1,196,500 |
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1.53–1.86 |
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1.64 |
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Options exercised
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— |
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(11,603 |
) |
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0.79–1.44 |
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1.24 |
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Options canceled
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258,436 |
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(258,436 |
) |
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0.79–1.88 |
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1.38 |
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Balances, December 31, 2011
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1,077,784 |
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3,672,179 |
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$ |
0.42–3.18 |
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$ |
1.45 |
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Additional shares reserved
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1,250,000 |
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— |
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Options granted
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(1,844,000 |
) |
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1,844,000 |
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1.38–7.75 |
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6.24 |
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Options exercised
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— |
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(402,580 |
) |
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0.79–3.08 |
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1.39 |
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Options canceled
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14,627 |
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(14,627 |
) |
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0.79–6.18 |
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4.25 |
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Balances, December 31, 2012
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498,411 |
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5,098,972 |
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$ |
0.42–7.75 |
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$ |
3.18 |
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Additional shares reserved
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1,250,000 |
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— |
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Options granted
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(1,663,500 |
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1,663,500 |
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4.45–5.58 |
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$ |
5.10 |
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Options exercised
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— |
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(145,641 |
) |
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0.79–3.46 |
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$ |
1.56 |
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Options canceled
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90,325 |
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(90,325 |
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1.44–7.75 |
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$ |
6.49 |
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Balances, December 31, 2013
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175,236 |
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6,526,506 |
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$ |
0.42–7.75 |
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$ |
3.66 |
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| Stock Options Outstanding and Exercisable by Exercise Price |
At December 31, 2013, stock options outstanding and
exercisable by exercise price were as follows:
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Range of
Exercise
Prices |
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Options Outstanding |
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Options Exercisable |
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Number
Outstanding |
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Weighted
Average
Remaining
Contractual
Life (Years) |
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Weighted
Average
Exercise
Price |
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Number
Exercisable |
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Weighted
Average
Exercise
Price |
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| $0.42 – 1.38 |
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570,518 |
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4.22 |
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$ |
1.11 |
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549,684 |
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$ |
1.10 |
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| $1.44 – 1.44 |
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1,377,739 |
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6.33 |
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1.44 |
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1,230,281 |
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1.44 |
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| $1.49 – 1.64 |
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1,124,003 |
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7.36 |
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1.63 |
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715,809 |
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1.63 |
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| $1.64 – 5.06 |
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667,309 |
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8.30 |
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3.82 |
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275,519 |
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3.13 |
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| $5.09 – 5.09 |
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1,185,000 |
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9.19 |
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5.09 |
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236,249 |
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5.09 |
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| $5.25 – 6.85 |
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690,937 |
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8.58 |
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6.14 |
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348,592 |
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6.22 |
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| $7.00 – 7.75 |
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911,000 |
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8.32 |
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7.26 |
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366,536 |
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7.25 |
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| $0.42 – 7.75 |
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6,526,506 |
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7.56 |
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$ |
3.66 |
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3,722,760 |
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$ |
2.80 |
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| Stock-Based Compensation Expense |
Stock-based compensation expense, which consists of the
compensation cost for employee stock options and ESPP, and the
value of options issued to non-employees for services rendered, was
allocated to research and development and general and
administrative in the consolidated statements of operations as
follows (in thousands):
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Year Ended
December 31, |
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2013 |
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2012 |
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2011 |
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Stock-based compensation expense:
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Research and development
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$ |
2,562 |
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$ |
1,521 |
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$ |
471 |
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General and administrative
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2,360 |
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1,489 |
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568 |
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$ |
4,922 |
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$ |
3,010 |
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$ |
1,039 |
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| Weighted-Average Fair Value Valuation Assumptions |
The fair value of employee stock options and employee purchase
rights under the Company’s ESPP was estimated using the
following weighted-average assumptions for the years ended
December 31, 2013, 2012 and 2011:
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Years ended
December 31, |
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2013 |
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2012 |
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2011 |
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Employee Stock Options
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Risk-free interest rate
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1.14 |
% |
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1.12 |
% |
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1.88 |
% |
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Expected life (in years)
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5.97 |
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5.99 |
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5.98 |
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Dividend yield
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— |
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— |
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— |
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Volatility
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101 |
% |
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105 |
% |
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92 |
% |
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Weighted-average fair value of stock options granted
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$ |
4.04 |
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$ |
5.09 |
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$ |
1.23 |
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Employee Stock Purchase Plan
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Risk-free interest rate
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0.19 |
% |
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0.21 |
% |
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0.15 |
% |
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Expected life (in years)
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1.25 |
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1.25 |
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1.25 |
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Dividend yield
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— |
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— |
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— |
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Volatility
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77 |
% |
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111 |
% |
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80 |
% |
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Weighted-average fair value of ESPP purchase rights
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$ |
2.27 |
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$ |
3.46 |
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$ |
0.66 |
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| Assumptions of Equity-Based Payments to Non-Employees |
Equity-Based Payments to Non-Employees using the following
assumptions:
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Years Ended December 31,
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2013 |
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2012 |
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2011 |
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Risk-free interest rate
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2.51 |
% |
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1.93 |
% |
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1.37 |
% |
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Expected life (in years)
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10 |
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10 |
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5.15 |
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Dividend yield
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— |
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— |
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— |
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Expected volatility
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100 |
% |
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101 |
% |
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92 |
% |
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