of revenue for the three months ended June 30, 2019. The $48.5 million increase in product revenue for the three month period ending June 30, 2020, in comparison to the same period in 2019, was primarily driven by an increase in the number of systems sold.
A portion of our revenue from systems sales is deferred until installation and other services related to future performance obligations are performed. The total amount of deferred revenue at June 30, 2020 and December 31, 2019 was $30.4 million and $29.3 million, respectively. The net increase in deferred revenue was primarily due to the collection of advance payments on systems.
Services
Services revenue, which includes the labor component of maintenance and service contracts and fees for service hours provided by on-site service personnel, was $5.8 million, or 4.7% of revenue for the three months ended June 30, 2020, compared with $5.6 million, or 7.5% of revenue for the three months ended June 30, 2019. Although services revenue typically increases with the expansion of the installed base of systems, it can fluctuate from period to period based on capacity utilization at customers’ manufacturing facilities, which affects the need for equipment service.
Six months ended June 30, 2020 Compared with Six months ended June 30, 2019
Product
Product revenue was $229.3 million, or 94.8% of revenue during the six months ended June 30, 2020, compared with $152.9 million, or 92.2% of revenue for the six months ended June 30, 2019. The $76.4 million increase in product revenue for the six month period ended June 30, 2020, in comparison to the same period in 2019, was primarily driven by an increase in the number of systems sold.
Services
Services revenue was $12.6 million, or 5.2% of revenue for the six months ended June 30, 2020, compared with $12.9 million, or 7.8% of revenue for the six months ended June 30, 2019.
Revenue Categories used by Management
In addition to the line item revenue categories discussed above, management also regularly disaggregates revenue in the following categories, which it finds relevant and useful:
●Ion implant revenue separate from revenue from legacy non-implant product lines, given that ion implantation systems are the primary driver of our growth and strategic objectives;
●Systems and Aftermarket revenues, in which “Aftermarket” is
A.the portion of Product revenue relating to spare parts, product upgrades and used equipment combined with
B.Services revenue, which is the labor component of Aftermarket revenues;
Aftermarket purchases reflect current fab utilization as opposed to Systems purchases which reflect capital investment decisions by our customers, which have differing economic drivers;
●Revenue by geographic regions, since economic factors impacting customer purchasing decisions may vary by geographic region; and
●Revenue by our customer market segments, since they can be subject to different economic drivers at different periods of time, impacting a customer’s likelihood of purchasing capital equipment during any particular period. Currently, management references three customer market segments: memory, mature technology processes and leading edge foundry and logic.