Year ended March 31,
Year ended March 31,
Period-to-period change
Period-to-period change
2019
2018
Amount  
% Change
(dollars in thousands) 
(dollars in thousands) 
(dollars in thousands) 
(dollars in thousands) 
Operating expenses:                
Research and development
$57,939
$38,373
$19,566
51%
Sales and marketing
139,194
121,246
17,948
15%
General and administrative
53,759
36,989
16,770
45%
Impairment of long-lived assets  
—
1,712
(1,712)
nm 
Restructuring  
(170)
832
(1,002)
nm 
Total operating expenses
$250,722
$199,152
$51,570
26%
operating expenses .
nm — not meaningful .
research and development expenses .
research and development expenses increased $ 19 .
6 million in the year ended march 31 2019 compared to the year ended march 31 2018 which was primarily attributable to increases in personnel-related costs of $ 11 .
8 million share-based compensation expense of $ 3 .
6 million and information technology and facility costs of $ 1 .
6 million .
research and development expenses for the year ended march 31 2019 as compared to the year ended march 31 2018 were positively impacted by approximately $ 0 .
5 million primarily as a result of the strengthening of the u .
s .
dollar relative to the british pound .
personnel-related cost increased primarily as a result of salaries and benefits associated with increased headcount throughout the year share-based compensation expense increased primarily as a result of share option grants since the prior year and information technology and facility costs increased primarily as a result of increased headcount .
sales and marketing expenses .
sales and marketing expenses increased $ 17 .
9 million in the year ended march 31 2019 compared to the year ended march 31 2018 which was primarily attributable to increases in information technology and facilities costs of $ 5 .
3 million personnel-related costs of $ 4 .
0 million share-based compensation expense of $ 3 .
4 million professional services of $ 2 .
7 million travel and other costs of $ 1 .
2 million and marketing costs of $ 1 .
1 million .
sales and marketing expenses for the year ended march 31 2019 as compared to the year ended march 31 2018 were positively impacted by approximately $ 1 .
5 million primarily as a result of the strengthening of the u .
s .
dollar relative to the australian dollar south african rand and british pound .
information technology and facilities costs and travel and other costs increased primarily as a result of increased headcount .
personnel-related costs increased primarily as a result of salaries and benefits associated with increased headcount and commissions partially offset by the impact of adopting asc 606 which resulted in capitalizing $ 13 .
8 million of commissions that would have been expensed under the prior accounting rules .
share-based compensation expense increased primarily as a result of share option grants since the prior year .
professional services costs increased primarily due to increased consulting fees .
general and administrative expenses .
general and administrative expenses increased $ 16 .
8 million in the year ended march 31 2019 compared to the year ended march 31 2018 which was primarily attributable to increases in personnel-related costs of $ 6 .
3 million share-based compensation expense of $ 5 .
8 million information technology and facilities costs of $ 1 .
9 million professional services costs of $ 1 .
2 million and litigation-related expenses of $ 1 .
0 million .
personnel-related costs increased primarily as a result of salaries and benefits associated with increased headcount .
share-based compensation expense increased primarily as a result of share option grants since the prior year and to a lesser extent the impact of share option modifications .
information technology and facility costs increased primarily as a result of increased headcount .
professional services costs increased primarily due to acquisition-related expenses .
restructuring and impairment of long-lived assets .
in the second quarter of fiscal 2019 we recorded a revision to restructuring expense of $ 0 .
2 million related to the exit of our watertown massachusetts corporate office space .
in the fourth quarter of fiscal 2018 upon the exit of our watertown massachusetts corporate office space we recorded a restructuring charge of $ 0 .
8 million for the remaining non-cancelable rent and estimated operating expenses for the vacated premises net of sublease rentals and we recorded a non-cash impairment charge of $ 1 .
7 million primarily related to leasehold improvements .

Question: What caused the share-based compensation expense to increase?
Answer: primarily as a result of share option grants since the prior year and to a lesser extent the impact of share option modifications.