ggplot2 panel graph is slightly off compared to others - r

Question

I am aligning line graphs in a panel. First one is slightly off compared to the other two (see figure). I have similar problems with the same kind of graph in other cases (in the other cases, the graph in question is the second one, and in all cases it is labeled as "study 2). I am using ggplot 2:
Setting up data & theme:
library(ggplot2)
# common theme used by all plots
theme1 <- theme(plot.title = element_text(hjust = 0.5, size = 20, face = "italic"),
legend.position = c(0.5,0.2),
legend.text=element_text(size=10, face="bold", color="black"),
legend.title = element_blank(),
legend.key.size = unit(2.5, "line"),
axis.text.x = element_text(angle = 45, hjust = 1, vjust = 1, face = "bold", size=15, color="black"),
panel.background = element_rect(fill = "white"),
axis.title.x=element_blank(),
axis.title.y = element_blank(),
axis.ticks.length = unit(0.2, "cm"),
axis.text.y = element_text(size = 18, colour="black"),
panel.border = element_rect(colour = "black", fill=NA, size=3),
panel.grid.major = element_line(size=0.2, colour = "gray", linetype="solid"),
panel.grid.minor.y =element_line(size=0.2, colour = "gray", linetype="solid"),
aspect.ratio = 4,
plot.margin = unit(c(0,0,0,2),"cm"))
# data for first plot
N300 <- data.frame(evaluation=rep(c("Low\nSalary\n($20k)", "High\nSalary\n($50k)"),
each = 2),
values =c(4.56, 4.20, 5.12, 4.55),
Condition =rep(c("High Ratio (200:1)", "Low Ratio (50:1)")))
# data for second plot
dfie2 <- data.frame(values = c(3.86, 3.94, 3.64),
condition = c("Baseline (300:1)", "CEO Lower (100:1)", "Median higher (100:1)"))
# data for third plot
dfie3 <- data.frame(evaluation=rep(c("Joint", "Separate"), each = 3),
values = c(5.03, 4.24, 4.43, 5.05, 5.21, 4.97),
Condition = rep(c("Baseline (400:1)", "CEO Lower (160:1)", "Median Higher (160:1)")))
Plot:
# first plot
Oldstudy <- ggplot(data=N300, aes(x=Condition, y=values, group=evaluation, label=values)) +
ggtitle("Study 2")+
geom_line(aes(linetype=evaluation), size=1.5) +
geom_point(shape=20, size=5) +
scale_y_continuous(breaks=c(1,2,3,4,5,6,7), limits=c(1,7))+
scale_linetype_manual(values=c("solid", "dotdash")) +
theme1
# second plot
France <- ggplot(data=dfie2, aes(x=condition, y=values, group=1)) +
ggtitle("Study 3")+
geom_line(size=1.5)+
#geom_text(aes(label=values), vjust=2, fontface="bold", size=5)+
geom_point(shape=20, size=5)+
scale_y_continuous(breaks=c(1,2,3,4,5,6,7), limits=c(1,7))+
theme1
# third plot
JS <- ggplot(data=dfie3, aes(x=Condition, y=values, group=evaluation)) +
ggtitle("Study 4")+
geom_line(aes(linetype=evaluation), size=1.5)+
geom_point(shape=20, size=5)+
scale_y_continuous(breaks=c(1,2,3,4,5,6,7), limits=c(1,7))+
scale_linetype_manual(values=c("solid", "dotted"))+
theme1
#### combine graphs ####
library(grid)
library(gridExtra)
grid.arrange(Oldstudy, France, JS, nrow = 1,
top = textGrob("Support for Lowering CEO compensation",
gp = gpar(fontface = "bold", fontsize = 20)
))
This is the plot that the code generates:

Answer 1

It looks like the three plots are being aligned by their middle points, which is causing the first one to look misaligned as it has shorter X-axis labels than the other two.
Instead of using the grid.arrange() function, you could try using the plot_grid() function of the cowplot package instead, which should align the plots by their axes instead of centring each one.

Answer 2

(Please note that I've done a considerable amount of cleaning / steamlining on the code included in your question. You are, of course, free to roll back the edit if you feel it misrepresents your problem, but I second what #camille mentioned in her comment that your original code had too many unnecessary details. While terse code can be hard to read, & comments help a reader understand what a piece of code is trying to do, peppering EVERY line with comments is generally a step too far.)
library(cowplot)
# just the plots, arranged horizontally
joint.plot <- plot_grid(Oldstudy, France, JS, nrow = 1, align = "h", axis = "tb")
# define joint title
plot.title <- ggdraw() +
draw_label("Support for Lowering CEO compensation",
fontface = 'bold', size = 20)
# combine the title & the joint plots vertically
plot_grid(plot.title, joint.plot,
ncol = 1,
rel_heights = c(0.1, 1)) # adjust relative height of title vs plot as needed