The tradeoff between equality and efficiency

WSJ reports on Arthur Okun's famous "leaky bucket" metaphor:

[Since] 1980, the American elite began to earn vastly higher incomes while workers outside the top quintile of earners endured a period of relative stagnation.  [Note the use of the term "relative."  Income in all quintiles has increased].  ...The share of income captured by the top 1% has grown from 8% to 20%. ...

Policies intended to fix inequality often have costly side effects, ... Social policies were like buckets—but they were leaky buckets. For every dollar expended, policies to aid the poor might deliver only 80 or 90 cents. Buckets with the biggest leaks could squander most of the benefits. The leak could result from poorly designed incentives or from inefficiency. Okun’s point was that policy makers should devise programs that get the best of this trade-off—those with the smallest leaks

In general, Conservatives accept this tradeoff, but Progressives do not:

According to Jason Furman, a former Obama adviser, “Forty years of progressives have defined themselves around the rejection of this [leaky bucket] metaphor, arguing that inequality-reducing policies promote economic growth by allowing people to better utilize their human capital.”