What are the main differences between commercial and investment banking?
Commercial banking relates to deposit-taking and lending whereas investment banking is predominantly a securities business. Traditionally commercial banking was viewed as relatively less risky than the more volatile investment banking business. Commercial bank performance was very much linked to economic growth and credit demand whereas investment bank performance is strongly influenced by stock market performance.
In many regions/ jurisdictions commercial banking and investment banking have been legally separated. For instance, in the US, the 1933 Glass-Steagall Act prohibited commercial banks from carrying out investment banking and insurance business. This legislation was put in place by the US authorities in response to the 1929 Wall Street Crash where excessive bank securities speculation was blamed for the crash and the Great Depression that followed.
Similar legislation was put in place in Japan in 1948. This legislation was repealed in 1999 in both countries. Banks in the EU have been allowed to offer commercial and investment banking services without restriction since 1992.
Note that many commercial banks do investment banking business although the latter is not considered the main business area.