{"pre_text": ["asset category target allocation total quoted prices in active markets for identical assets ( level 1 ) significant observable inputs ( level 2 ) significant unobservable inputs ."], "post_text": ["balance as of january 1 , 2017 .", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", "$ 140 actual return on assets .", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", "2 purchases , issuances and settlements , net .", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", "136 balance as of december 31 , 2017 .", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", ".", "$ 278 the company 2019s postretirement benefit plans have different levels of funded status and the assets are held under various trusts .", "the investments and risk mitigation strategies for the plans are tailored specifically for each trust .", "in setting new strategic asset mixes , consideration is given to the likelihood that the selected asset allocation will effectively fund the projected plan liabilities and meet the risk tolerance criteria of the company .", "the company periodically updates the long-term , strategic asset allocations for these plans through asset liability studies and uses various analytics to determine the optimal asset allocation .", "considerations include plan liability characteristics , liquidity needs , funding requirements , expected rates of return and the distribution of returns .", "in 2012 , the company implemented a de-risking strategy for the american water pension plan after conducting an asset-liability study to reduce the volatility of the funded status of the plan .", "as part of the de-risking strategy , the company revised the asset allocations to increase the matching characteristics of fixed- income assets relative to liabilities .", "the fixed income portion of the portfolio was designed to match the bond- ."], "table": [["", "level 3"], ["balance as of january 1 2018", "$ 278"], ["actual return on assets", "-23 ( 23 )"], ["purchases issuances and settlements net", "-25 ( 25 )"], ["balance as of december 31 2018", "$ 230"]], "table_ori": [["", "Level 3"], ["Balance as of January 1, 2018", "$278"], ["Actual return on assets", "(23)"], ["Purchases, issuances and settlements, net", "(25)"], ["Balance as of December 31, 2018", "$230"]]}

Question: by what percentage level 3 balance decrease during 2018?
Evidence:
table_4: the balance as of december 31 2018 of level 3 is $ 230 ;
table_1: the balance as of january 1 2018 of level 3 is $ 278 ;
Program: subtract(230, 278), divide(#0, 278)
Answer:
str_answer: -17.3%
exe_answer: -0.17266