According to the charts put out by the census bureau, the median household income in 2015 = 56,516, while the median household income in 1999 = 57,909. In other words, despite the "amazing growth" in household income in 2015, household income by 2015 still wasn't as high as it was 16 years before that. What the heck is there to celebrate about that?
Remember, this is household income, not individual income. So the entire household, which may include several wage-earners, is getting by on an income level that is actually lower than it was in 1999, while basic expenses (food, housing, healthcare, etc.) has continually increased over the years. One third of people aged 21 - 34 still live with their parents; a level never before seen in this country, even during the Great Depression of the 1930's. They may be working some sort of job, but can't afford to live on their own. So, yeah, that would increase household income.
Also, the census bureau changed the way they worded their questions to create their reports for this period, and even included a disclaimer (that the media didn't bother to read) that this report might not be accurate.
See this for an accurate deconstruction of the report: http://www.declineoftheempire.com/2016/09/deconstructing-median-income-bullshit.html#more