jsonlite vs rjsonion - can we make jsonlite faster?

benchmark.R

library(microbenchmark)

# json test is a character vector of length 2 containing
# both of the json elements given in sample_data.json

microbenchmark(
  lite <- lapply(json_test,function(x){
    jsonlite::fromJSON(x,simplifyVector = F)
  }),
  SONIO <- lapply(json_test,function(x){
    RJSONIO::fromJSON(x)
  })
)

sample_data.json

{
    "ts_key": "some_data_A",
    "ts_data": {
        "1999-10-01": "22.62487757",
        "2000-01-01": "33.99014778",
        "2000-04-01": "41.50197628",
        "2000-07-01": "54.50191571",
        "2000-10-01": "51.77713737",
        "2001-01-01": "48.32214765",
        "2001-04-01": "38.15533981",
        "2001-07-01": "24.24830262",
        "2001-10-01": "-51.31450828",
        "2002-01-01": "-49.51830443",
        "2002-04-01": "-34.0776699",
        "2002-07-01": "-47.81341108",
        "2002-10-01": "-101.3207547",
        "2003-01-01": "-80.74003795",
        "2003-04-01": "-98.69158879",
        "2003-07-01": "-89.83208955",
        "2003-10-01": "-63.53488372",
        "2004-01-01": "-56.05214153",
        "2004-04-01": "-26.22180451",
        "2004-07-01": "-19.49860724",
        "2004-10-01": "-30.91922006",
        "2005-01-01": "-28.20037106",
        "2005-04-01": "-24.03393025",
        "2005-07-01": "-35.31100478",
        "2005-10-01": "-33.05164319",
        "2006-01-01": "0",
        "2006-04-01": "15.46589817",
        "2006-07-01": "34.31839847",
        "2006-10-01": "41.06280193",
        "2007-01-01": "43.56530029",
        "2007-04-01": "48.1086324",
        "2007-07-01": "43.49056604",
        "2007-10-01": "35.71428571",
        "2008-01-01": "30.67426401",
        "2008-04-01": "2.36294896",
        "2008-07-01": "-25.09469697",
        "2008-10-01": "-57.4108818",
        "2009-01-01": "-63.98503274",
        "2009-04-01": "-96.30655586",
        "2009-07-01": "-100.2782931",
        "2009-10-01": "-74.69654528",
        "2010-01-01": "-58.29471733",
        "2010-04-01": "-7.358490566",
        "2010-07-01": "5.272895467",
        "2010-10-01": "15.72617946",
        "2011-01-01": "16.65089877",
        "2011-04-01": "12.79178338",
        "2011-07-01": "-5.096153846",
        "2011-10-01": "-41.62679426",
        "2012-01-01": "-47.11359404",
        "2012-04-01": "-17.66190076",
        "2012-07-01": "-24.13793103",
        "2012-10-01": "-21.98088619",
        "2013-01-01": "-9.739714526",
        "2013-04-01": "-6.623735051",
        "2013-07-01": "-9.212880143",
        "2013-10-01": "2.72479564",
        "2014-01-01": "11.82885906",
        "2014-04-01": "5.45625588",
        "2014-07-01": "6.925207756",
        "2014-10-01": "-8.97994769",
        "2015-01-01": "0.928505107",
        "2015-04-01": "-21.99612403",
        "2015-07-01": "-35.59670782",
        "2015-10-01": "-29.56273764",
        "2016-01-01": "-34.69041561"
    },
    "ts_frequency": 4
}

{
    "ts_key": "more_data_B",
    "ts_data": {
        "1999-10-01": "29.6566077",
        "2000-01-01": "37.33333333",
        "2000-04-01": "39.37172775",
        "2000-07-01": "44.52405322",
        "2000-10-01": "31.32154006",
        "2001-01-01": "29.45891784",
        "2001-04-01": "12.06185567",
        "2001-07-01": "9.799789252",
        "2001-10-01": "-59.91735537",
        "2002-01-01": "-3.756345178",
        "2002-04-01": "4.756980352",
        "2002-07-01": "-12.21294363",
        "2002-10-01": "-34.5",
        "2003-01-01": "-22.89395441",
        "2003-04-01": "-28.26961771",
        "2003-07-01": "-16.2027833",
        "2003-10-01": "-4.015670911",
        "2004-01-01": "20.61068702",
        "2004-04-01": "24.03100775",
        "2004-07-01": "15.03394762",
        "2004-10-01": "-3.875968992",
        "2005-01-01": "5.152671756",
        "2005-04-01": "2.152641879",
        "2005-07-01": "-12.46261216",
        "2005-10-01": "-11.9140625",
        "2006-01-01": "24.52452452",
        "2006-04-01": "18.96207585",
        "2006-07-01": "24.89959839",
        "2006-10-01": "19.46721311",
        "2007-01-01": "25.57442557",
        "2007-04-01": "30.67484663",
        "2007-07-01": "22.03721841",
        "2007-10-01": "11.78781925",
        "2008-01-01": "-9.190809191",
        "2008-04-01": "-19.34846989",
        "2008-07-01": "-45.02463054",
        "2008-10-01": "-60.50583658",
        "2009-01-01": "-57.35150925",
        "2009-04-01": "-64.04602109",
        "2009-07-01": "-32.62955854",
        "2009-10-01": "18.33810888",
        "2010-01-01": "23.71916509",
        "2010-04-01": "43.94966118",
        "2010-07-01": "33.14231137",
        "2010-10-01": "18.86255924",
        "2011-01-01": "15.04424779",
        "2011-04-01": "14.17475728",
        "2011-07-01": "-21.6080402",
        "2011-10-01": "-37.5502008",
        "2012-01-01": "-29.31533269",
        "2012-04-01": "-1.977644024",
        "2012-07-01": "-19.57720588",
        "2012-10-01": "-23.1375986",
        "2013-01-01": "-0.255972696",
        "2013-04-01": "3.305785124",
        "2013-07-01": "-5.621033545",
        "2013-10-01": "1.39275766",
        "2014-01-01": "17.64705882",
        "2014-04-01": "7.830188679",
        "2014-07-01": "4.944029851",
        "2014-10-01": "-13.50877193",
        "2015-01-01": "-12.27573182",
        "2015-04-01": "-7.593688363",
        "2015-07-01": "-24.71204188",
        "2015-10-01": "-15.63106796",
        "2016-01-01": "-15.69817866"
    },
    "ts_frequency": 4
}