Table:
|  | December 31, |  |
| --- | --- | --- |
| (in millions, except percentages) | 2019 | 2018 |
| Total ARR | $179.5 | $162.6 |
| Year-over-year percentage increase | 10% | 20% |
| Subscription ARR | $113.9 | $95.9 |
| Year-over-year percentage increase | 19% | 32% |
| Perpetual license support ARR | $65.6 | $66.7 |
| Year-over-year percentage increase (decrease) | (2)% | 6% |
Paragraphs:
Annual Recurring Revenue
Beginning with the fourth quarter of 2018, we began monitoring a new operating metric, total annual recurring revenue (“Total ARR”), which is defined as the annualized value of all recurring revenue contracts active at the end of a reporting period. Total ARR includes the annualized value of subscriptions (“Subscription ARR”) and the annualized value of software support contracts related to perpetual licenses (“Perpetual license support ARR”) active at the end of a reporting period and does not include revenue reported as perpetual license or professional services in our consolidated statement of operations. We are monitoring these metrics because they align with how our customers are increasingly purchasing our solutions and how we are managing our business. These ARR measures should be viewed independently of revenue, unearned revenue, and customer arrangements with termination rights as ARR is an operating metric and is not intended to be combined with or replace those items. ARR is not an indicator of future revenue and can be impacted by contract start and end dates and renewal rates.
ARR metrics as of December 31, 2019 and 2018 were as follows (unaudited):
Question:
When did the company start monitoring total annual recurring revenue? 
Answer: Beginning with the fourth quarter of 2018