Wall Street regulators have imposed far lower penalties in the first six months of Donald Trump’s presidency than they did during the first six months of 2016, a comparable period in the Obama administration, according to a Wall Street Journal analysis.

Lawyers who defend financial cases said a shift to a business-friendly stance at regulatory agencies in the Trump administration is one of several reasons for the decrease. Other factors include delays resulting from the change in administrations and the winding down of cases...