$15.5B market cap Wednesday to S&P500's ~$32.3T. If you held the S&P500, you lost about 0.05% when SIVB got zeroed. In comparison, S&P500 was down 1.45% Friday. (Almost all of the impact to your retirement from SVB's failure will be from indirect effects, like downswings in other bank stocks, rather than direct losses from SIVB. Unless you held a highly concentrated position in SIVB.)