# Create indicators
df$married_women <- ifelse(df$worker == 2, 1, 0)
df$treated3 <- ifelse(df$experimental == 1 & df$married_women == 1, 1, 0)

# Triple diff event study regression
lm(earnings ~ experimental*married_women + 
     year*experimental + 
     year*married_women + 
     treated3*relevel(factor(year), ref = "2014"), 
   data = df)