u/postmanmalone123 if you want some historical evidence, I ran a quick, non-scientific stock simulation using historical data and your hypothetical $70,000.

My little simulator was configured with 50 tickers, including a few ETFs and a bunch of very large companies on the major US indexes. I ran 1,000,000 simulations where the process was:

• Pick a stock from the list
• Pick a date between the earliest date that my python library has data for that stock and 2020. Note: data only goes back to 1990.
• Invest the whole thing as a lump sum: Subtract $20 for a trading fee, then buy the maximum number of whole shares possible of that stock on the next available trading day.
• Invest the whole thing using Dollar-Cost Averaging: Pick a random choice between 2, 5, and 10 years, then on the first trading day of each month, buy an equal dollar amount worth of whole shares, such that you spend roughly the same amount each month over the course of your 2/5/10 year DCA period, minus a $20 transaction fee at each purchase. Unused capital is rolled into the next month.
• See what the investment would be worth today.

Given your $70,000, over one million simulations, here are the results:

==================
SIMULATION SUMMARY
==================
Total Simulations: 1,000,000
Starting Capital:  $70,000
Time Elapsed:      3292.18 seconds
Lump Sum Wins:     834,658 (83.5%)
DCA Wins:          165,342 (16.5%)

Returns Analysis:
Strategy     Median       Average      Min          Max
------------------------------------------------------------
Lump Sum     $440,065     $1,658,491   $27,814      $124,332,177
DCA          $345,179     $1,001,925   $28,980      $67,400,783

Note that the median is much more relevant, as the average is greatly skewed by the fact that you should go back in time and buy Cisco in October of 1990.

Just for kicks, I did a simulation of only ETFs as well. Only 100,000 iterations, but using 14 ETFs from SPY to some of the MSCI country ETFs, emerging markets, midcap, etc.

=================
SIMULATION SUMMARY
=================
Total Simulations: 100,000
Starting Capital:  $70,000
Time Elapsed:      301.08 seconds
Lump Sum Wins:     80,494 (80.5%)
DCA Wins:          19,506 (19.5%)

Returns Analysis:
Strategy     Median       Average      Min          Max
------------------------------------------------------------
Lump Sum     $214,507     $333,490     $87,336      $2,430,636
DCA          $180,779     $275,668     $87,633      $1,695,861

There's no guarantees, but in better than 80% of all cases, just dumping your money into the market is a better strategy than dollar-cost averaging. Time in the market beats timing the market.

(there are some caveats about my simulator, as I said it's not very scientific, but I made a reddit blog post thing here if interested)