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Financial leverage

As explained in Build a Robo-Advisor with Python (From Scratch)

Leverage is the use of borrowed funds to increase the size of an investment position relative to the investor's own capital.

Financial leverage increases an investment position beyond the investor’s own capital by borrowing funds or scaling portfolio weights above 100%. It can raise expected return, but it also introduces borrowing costs, margin restrictions, collateral risk, and possible forced sales. section 11.3.1 section 2.4

Scaling a risk-parity portfolio

A risk-parity portfolio with 4.7% volatility can be scaled to match a 60/40 portfolio’s 10.3% volatility. Scaling its weights above 100% is leverage; achieving that exposure requires borrowing, and the scaled portfolio has an expected return of 4.36%. section 11.3.1

Leverage requires balancing exposure against financing and liquidation risks:

  • Purchase securities on margin, using the purchased assets as collateral. section 11.3.1
  • Account for borrowing rates, typically described as 2%–3% above the current risk-free rate. section 11.3.1
  • Expect brokerage limits, cash-deposit requirements, or forced sales when portfolio values fall sufficiently. section 11.3.1
  • Choose leverage according to the desired risk and return trade-off; no single amount is universally correct. section 11.3.1
w_rp_scaled = w_rp * 10.3 / 4.7

Scales risk-parity weights by the ratio between target volatility and unlevered volatility. section 11.3.1

w_rp_scaled @ mu

Calculates the expected return of the scaled portfolio from its adjusted weights and expected asset returns. section 11.3.1

How Build a Robo-Advisor with Python (From Scratch) covers it

How deep it goes
Explains scaling, margin mechanics, financing costs, and liquidation risks, but defers institutional derivatives-based leverage.
Examples
Uses scaled risk-parity weights, a 60/40 comparison, and a $1 million portfolio borrowing $500,000 for a $1.5 million tangent-portfolio position.
What it assumes
Assumes portfolio weights, volatility, expected returns, and risk-free assets, while introducing borrowing and margin implications directly.
What you can do after
Apply it via margin borrowing or a risk-free asset to scale exposure while accounting for interest costs and margin calls.
How it connects
Connects leverage to risk parity, portfolio construction, the risk-free asset, the capital allocation line, and the tangent portfolio.

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This explainer was generated by Manning's knowledge graph from the text of Build a Robo-Advisor with Python (From Scratch). The section links point to the parts of the book it draws on.