Read the following texts and table with financial data from an S&P 500 earnings report carefully.Based on the question-answer history (if provided), answer the last question. The answer may require mathematical calculation based on the data provided.


unconditional purchase obligations approximately $ 390 of our long-term unconditional purchase obligations relate to feedstock supply for numerous hyco ( hydrogen , carbon monoxide , and syngas ) facilities . the price of feedstock supply is principally related to the price of natural gas . however , long-term take-or-pay sales contracts to hyco customers are generally matched to the term of the feedstock supply obligations and provide recovery of price increases in the feedstock supply . due to the matching of most long-term feedstock supply obligations to customer sales contracts , we do not believe these purchase obligations would have a material effect on our financial condition or results of operations . refer to note 17 , commitments and contingencies , to the consolidated financial statements for additional information on our unconditional purchase obligations . the unconditional purchase obligations also include other product supply and purchase commitments and electric power and natural gas supply purchase obligations , which are primarily pass-through contracts with our customers . in addition , purchase commitments to spend approximately $ 540 for additional plant and equipment are included in the unconditional purchase obligations in 2016 . we also purchase materials , energy , capital equipment , supplies , and services as part of the ordinary course of business under arrangements that are not unconditional purchase obligations . the majority of such purchases are for raw materials and energy , which are obtained under requirements-type contracts at market prices . obligation for future contribution to an equity affiliate on 19 april 2015 , a joint venture between air products and acwa holding entered into a 20-year oxygen and nitrogen supply agreement to supply saudi aramco 2019s oil refinery and power plant being built in jazan , saudi arabia . air products owns 25% ( 25 % ) of the joint venture and guarantees the repayment of its share of an equity bridge loan . in total , we expect to invest approximately $ 100 in this joint venture . as of 30 september 2015 , we recorded a noncurrent liability of $ 67.5 for our obligation to make future equity contributions based on advances received by the joint venture under the loan . income tax liabilities noncurrent deferred income tax liabilities as of 30 september 2015 were $ 903.3 . tax liabilities related to unrecognized tax benefits as of 30 september 2015 were $ 97.5 . these tax liabilities were excluded from the contractual obligations table , as it is impractical to determine a cash impact by year given that payments will vary according to changes in tax laws , tax rates , and our operating results . in addition , there are uncertainties in timing of the effective settlement of our uncertain tax positions with respective taxing authorities . refer to note 23 , income taxes , to the consolidated financial statements for additional information . pension benefits the company sponsors defined benefit pension plans and defined contribution plans that cover a substantial portion of its worldwide employees . the principal defined benefit pension plans 2014the u.s . salaried pension plan and the u.k . pension plan 2014were closed to new participants in 2005 and were replaced with defined contribution plans . over the long run , the shift to defined contribution plans is expected to reduce volatility of both plan expense and contributions . the fair market value of plan assets for our defined benefit pension plans as of the 30 september 2015 measurement date decreased to $ 3916.4 from $ 4114.6 at the end of fiscal year 2014 . the projected benefit obligation for these plans was $ 4787.8 and $ 4738.6 at the end of the fiscal years 2015 and 2014 , respectively . refer to note 16 , retirement benefits , to the consolidated financial statements for comprehensive and detailed disclosures on our postretirement benefits . pension expense . <table class='wikitable'><tr><td>1</td><td>-</td><td>2015</td><td>2014</td><td>2013</td></tr><tr><td>2</td><td>pension expense</td><td>$ 135.6</td><td>$ 135.9</td><td>$ 169.7</td></tr><tr><td>3</td><td>special terminations settlements and curtailments ( included above )</td><td>35.2</td><td>5.8</td><td>19.8</td></tr><tr><td>4</td><td>weighted average discount rate</td><td>4.0% ( 4.0 % )</td><td>4.6% ( 4.6 % )</td><td>4.0% ( 4.0 % )</td></tr><tr><td>5</td><td>weighted average expected rate of return on plan assets</td><td>7.4% ( 7.4 % )</td><td>7.7% ( 7.7 % )</td><td>7.7% ( 7.7 % )</td></tr><tr><td>6</td><td>weighted average expected rate of compensation increase</td><td>3.5% ( 3.5 % )</td><td>3.9% ( 3.9 % )</td><td>3.8% ( 3.8 % )</td></tr></table> .
Question: what was the fair market value of plan assets of the benefit pension plans in 2015?
Answer: 3916.4
Question: and what was it in 2014?
Answer: 4114.6
Question: what was, then, the change over the year?

-198.2