Two column headers with same borders

I'd love to have consistent borders on my kable table

Here's my data frame:

df1 <- data.frame(inst = c("A", "B", "C", "D", "E", "F", "G"), 
                   year_1_type1 = c(1,5,3,8,7,9,4), 
                   year_2_type1 = c(5,7,8,3,5,2,6), 
                   year_1_type2 = c(1,5,3,8,7,9,4), 
                   year_2_type2 = c(5,7,8,3,5,2,6))

And here is my table:

And here is the code:

 df1  %>%
     kbl(caption = '<b>Table 5</b>-Comparison of Types and Years', align='l',  
         col.names = c("inst", "year 1", "year 2", "year 1", "year 2")) %>%
     kable_classic(full_width = T, html_font = "Arial Narrow") %>% 
     kable_styling() %>%
     add_header_above(c(" " = 1, "Type 1" = 2, "Type 2"=2), align = "l", extra_css ="border-left: 1px solid;")

I definitely want the border to the left of Type 1 and Type 2 but it would be nice if it extended to the left of year 1 I tried adding extra_css ="border-left: 1px solid;" after the col.names function but that didn't work. Does anyone know how to add these borders?

You can extend the border by using column_spec(c(1:5),border_left = "1px solid") . However, this will not create border for the column headers. To add border to the headers, use extra_css: row_spec(0, extra_css ="border-left: 1px solid;"). Here is the final code:

df1  %>%
  kbl(caption = '<b>Table 5</b>-Comparison of Types and Years', align='l',  
      col.names = c("inst", "year 1", "year 2", "year 1", "year 2")) %>%
  kable_classic(full_width = T, html_font = "Arial Narrow") %>% 
  kable_styling() %>%
  column_spec(c(1:5),border_left = "1px solid") %>%
  row_spec(0, extra_css ="border-left: 1px solid;") %>%
  add_header_above(c(" " = 1, "Type 1" = 2, "Type 2"=2), align = "l", extra_css ="border-left: 1px solid;")