According to The Wall Street Journal:
Starting median salary: $38K
Mid-career median salary: $64.7K
Percent change from starting to mid-career salary: 70.3%
Mid-career 10th percentile salary (only 10% earn less than): $33.4K
Mid-career 25th percentile salary (25% earn less than): $44.8K
Mid-career 75th percentile salary (75% earn less than): $93.2K
Mid-career 90th percentile salary (90% earn less than): $133K
Well--nobody said you were going to get rich on an English degree! But you can see that there's a pretty respectable track record throughout one's career and lifetime earnings for English majors.
You can see the data in context with other majors at the link above.