pre_text: Key Operating Metrics and Non-GAAP Financial Measures We collect and analyze operating and financial data to evaluate the health of our business, allocate our
  
  resources, and assess our performance. In addition to revenue, net loss, and other results under  generally accepted accounting principles (GAAP), the following table sets forth key operating metrics and non-GAAP financial measures we use to evaluate our business. We believe these metrics and measures are useful to facilitate period-to-period comparisons of our business, and to facilitate comparisons of our performance to that of other payment processors. Each of these metrics and measures excludes the effect of our processing agreement with Starbucks which transitioned to another payments solutions provider in the fourth quarter of 2016. As we do not expect transactions with Starbucks to recur, we believe it is useful to exclude Starbucks activity to clearly show the impact Starbucks has had on our financial results historically. Our agreements with other sellers generally provide both those sellers and us the unilateral right to terminate such agreements at any time, without fine or
  
  penalty. Gross Payment Volume (GPV) We define GPV as the total dollar amount of all card payments processed by sellers using Square, net of refunds. Additionally, GPV includes Cash App activity related to peer-to-peer payments sent from a credit card and Cash for Business. As described above, GPV excludes card payments processed for Starbucks Adjusted Revenue Adjusted Revenue is a non-GAAP financial measure that we define as our total net revenue less transaction-based costs and bitcoin costs, and we add back the impact of the acquired deferred revenue adjustment, which was written down to fair value in purchase. This measure is also adjusted to eliminate the effect of activity with Starbucks, which ceased using our payments solutions altogether in the fourth quarter of 2016, and we believe that providing Adjusted Revenue metrics that exclude the impact of our agreement with Starbucks is useful to investors.
table: Year Ended December 31,
table: 2018 2017 2016 2015 2014
table: (in thousands, except for GPV and per share data)
table: Gross Payment Volume (GPV)(in millions) $84,654 $65,343 $49,683 $35,643 $23,780
table: Adjusted Revenue $1,587,641 $983,963 $686,618 $452,168 $276,310
table: Adjusted EBITDA $256,523 $139,009 $44,887 $(41,115) $(67,741)
table: Adjusted Net Income (Loss) Per Share:
table: Basic $0.55 $0.30 $0.04 $(0.39) $(0.62)
table: Diluted $0.47 $0.27 $0.04 $(0.39) $(0.62)
question: Analyse this data from a financial earnings document. How much is the change of adjusted EBITDA from 2015 to 2016?