労働集約型の製造業とは異なり、知識集約型産業では、労働者は特定のスキルを持ち、企業側に損害なく入れ替えをすることはできない
従業員がスキルを高め、退職をちらつかせて企業と賃金交渉する力を持つからだ

知識集約型産業では最底辺の給料に一律化させる方式を従業員が拒否するため労組にメリットはない

結論として労働集約型であっても会社側が部門・工場単位での閉鎖を決断すれば組合の存在は解雇になんら影響を与えない

whether the business criteria utilized to select employees for termination makes sense, and whether that criteria was applied consistently;
whether procedures in personnel policies related to terminations were followed;
whether the employees’ responsibilities were fully eliminated – if not, what happened to the responsibilities; and
whether anyone was hired to fulfill the terminated employees’ duties.

つまり部門・工場単位で閉鎖すれば誰もが平等のため恣意性が全く存在しなくなるということだが、
40歳の中高年を解雇して、40歳の中高年を同じ職に入れた場合は、差別と認められることはまずない

年齢でないように細心の注意を払い、能力不足を解雇理由とするなら、解雇は概ね問題なくできる

That’s not to say that plaintiffs hold all the cards -- far from it. When these lawsuits do get as far as a courtroom, employers usually prevail.
A 2009 Supreme Court case, Gross v. FBL Financial Services, Inc., raised the bar for proving age discrimination. Instead of merely showing that
age was a contributing factor in an employer’s decision to fire or demote them, or to refuse to hire them in the first place, plaintiffs now have
to come up with convincing evidence that age was the only factor.
“That is a lot harder,” Jackson observes, “because of course employers may have several different reasons for making any given decision, not
just one.” If, for example, the company can persuade a jury that you lost your job because you just weren’t that great at it -- whether you’re
30 or 80 -- then your chances of winning may be slim to none. And in an era of constant cost cutting, almost any company can point to many
money-saving moves and contend that your dismissal or demotion was a simple matter of dollars and cents.

なぜなら最高裁判決によって解雇理由が年齢だけだったことを証明する証拠の提示が必要となったからで
その難易度は高く企業側が無能を解雇理由とした場合それを否定するなら、明確な職務での成果が必要となる

反対にアメリカでは中高年が応募した場合に断る場合に訴訟を起こされるケースがある